Fix false negative result of test_ceph_metrics_available on Azure
Testcase `test_ceph_metrics_available` fails on Azure platform, on errors like:

```
20:17:27 - MainThread - test_monitoring_defaults - ERROR - failed to get results for ceph_rgw_get_initial_lat_count                                                                                                                                                              
20:17:36 - MainThread - test_monitoring_defaults - ERROR - failed to get results for ceph_rgw_get_b                                                                                                                                                                              
```

Which leads to the failure of the test:

```
E       AssertionError: OCS Monitoring should provide some value(s) for all tested metrics, so that the list of metrics without results is empty.                                                                                                                                
E       assert ['ceph_rgw_qlen',\\n 'ceph_rgw_req',\\n 'ceph_rgw_cache_miss',\\n 'ceph_rgw_put',\\n 'ceph_rgw_put_initial_lat_sum',\\n 'ceph_rgw_put_initial_lat_count',\\n 'ceph_rgw_keystone_token_cache_hit',\\n 'ceph_rgw_metadata',\\n 'ceph_rgw_qactive',\\n 'ceph_rgw_get_initial_l
at_sum',\\n 'ceph_rgw_get_initial_lat_count',\\n 'ceph_rgw_get_b',\\n 'ceph_rgw_failed_req',\\n 'ceph_rgw_keystone_token_cache_miss',\\n 'ceph_rgw_get',\\n 'ceph_rgw_cache_hit',\\n 'ceph_rgw_put_b'] == []                                                                            
E         Left contains 17 more items, first extra item: 'ceph_rgw_qlen'                                                                                                                                                                                                         
E         Full diff:                                                                                                                                                                                                                                                             
E           [                                                                                                                                                                                                                                                                    
E         +  ,                                                                                                                                                                                                                                                                   
E         -  'ceph_rgw_qlen',
E         -  'ceph_rgw_req',
E         -  'ceph_rgw_cache_miss',
E         -  'ceph_rgw_put',
E         -  'ceph_rgw_put_initial_lat_sum',
E         -  'ceph_rgw_put_initial_lat_count',
E         -  'ceph_rgw_keystone_token_cache_hit',
E         -  'ceph_rgw_metadata',
E         -  'ceph_rgw_qactive',
E         -  'ceph_rgw_get_initial_lat_sum',
E         -  'ceph_rgw_get_initial_lat_count',
E         -  'ceph_rgw_get_b',
E         -  'ceph_rgw_failed_req',
E         -  'ceph_rgw_keystone_token_cache_miss',
E         -  'ceph_rgw_get',
E         -  'ceph_rgw_cache_hit',
E         -  'ceph_rgw_put_b',
E           ]
```

But the fact that RGW is not deployed on Azure is expected, and we need to add Azure into `platforms_without_rgw` variable in the test case.
diff --git a/ocs_ci/ocs/constants.py b/ocs_ci/ocs/constants.py
index b5808061..25b75a2c 100644
--- a/ocs_ci/ocs/constants.py
+++ b/ocs_ci/ocs/constants.py
@@ -572,8 +572,9 @@ VDBENCH_MIN_CAPACITY = 300  # minimum storage capacity (in GB) for the test to r
 
 # Platforms
 AWS_PLATFORM = 'aws'
+AZURE_PLATFORM = 'azure'
 VSPHERE_PLATFORM = 'vsphere'
-CLOUD_PLATFORMS = (AWS_PLATFORM)
+CLOUD_PLATFORMS = (AWS_PLATFORM, AZURE_PLATFORM)
 
 # Default SC based on platforms
 DEFAULT_SC_AWS = "gp2"
diff --git a/tests/manage/monitoring/prometheusmetrics/test_monitoring_defaults.py b/tests/manage/monitoring/prometheusmetrics/test_monitoring_defaults.py
index f43e9286..ef8176f4 100644
--- a/tests/manage/monitoring/prometheusmetrics/test_monitoring_defaults.py
+++ b/tests/manage/monitoring/prometheusmetrics/test_monitoring_defaults.py
@@ -378,7 +378,6 @@ def test_ceph_metrics_available():
         "ceph_pool_recovering_keys_per_sec",
         "ceph_pool_recovering_objects_per_sec"]
 
-    platforms_without_rgw = [constants.AWS_PLATFORM]
     current_platform = config.ENV_DATA['platform'].lower()
 
     prometheus = PrometheusAPI()
@@ -394,7 +393,7 @@ def test_ceph_metrics_available():
             is_rgw_metric = (
                 metric.startswith("ceph_rgw")
                 or metric.startswith("ceph_objecter"))
-            if current_platform in platforms_without_rgw and is_rgw_metric:
+            if current_platform in constants.CLOUD_PLATFORMS and is_rgw_metric:
                 msg = (
                     f"failed to get results for {metric}, "
                     f"but it is expected on {current_platform}")
['tests/manage/monitoring/prometheusmetrics/test_monitoring_defaults.py', 'ocs_ci/ocs/constants.py']