MSUnmerged fails to parse T1_UK_RAL_Disk stats - root_failed error
**Impact of the bug**
MSUnmerged

**Describe the bug**
The T1_UK_RAL_Disk RSE has been enabled in the MSUnmerged service configuration, with that a new issue [1] got exposed with the `root_failed` attribute that we currently use to check whether the scanner succeeded checking the directories or not. Given that there is no scanner for RAL, but only a text file that needs to be downloaded, that key/value attribute does not exist in the `WM/stats` API output.

This issue has been discussed with Igor M., in the #cms-consistency channel and he suggests to use only the `status` attribute.
 
**How to reproduce it**
Checkout out the T1_UK_RAL_Disk output from WM/stats API

**Expected behavior**
Remove that check on `root_failed`:
https://github.com/dmwm/WMCore/blob/master/src/python/WMCore/MicroService/MSUnmerged/MSUnmerged.py#L406

and keep checking RSEs dump status based only on the `status` attribute (as already coded 2 lines above).

**Additional context and error message**
Quoting a short summary from the information provided by Igor M.
"""
The `status` attribute says whether the scanner failed or succeeded. The attribute value can be either “started” or “done” or “failed”.
For regular sites, status="failed" is equivalent to root_failed=true
For RAL it means that the site dump download has failed for this run 
“started” means the scanner has not finished yet
For RAL, it means that the site dump is still being downloaded
“done” means it scanned the whole tree, but in case of unmerged scanning, it does not necessarily mean that all subdirectories were scanned successfully.
For RAL it means that the site dump was downloaded successfully 
"""

[1]
```
2021-11-08 01:54:59,148:ERROR:MSUnmerged: plineUnmerged: General error from pipeline. RSE: T1_UK_RAL_Disk. Error: 'root_failed' Will retry again in the next cycle.
Traceback (most recent call last):
  File "/data/srv/HG2111a/sw/slc7_amd64_gcc630/cms/reqmgr2ms/0.5.5.pre3/lib/python3.8/site-packages/WMCore/MicroService/MSUnmerged/MSUnmerged.py", line 235, in _execute
    pline.run(MSUnmergedRSE(rseName))
  File "/data/srv/HG2111a/sw/slc7_amd64_gcc630/cms/reqmgr2ms/0.5.5.pre3/lib/python3.8/site-packages/Utils/Pipeline.py", line 140, in run
    return reduce(lambda obj, functor: functor(obj), self.funcLine, obj)
  File "/data/srv/HG2111a/sw/slc7_amd64_gcc630/cms/reqmgr2ms/0.5.5.pre3/lib/python3.8/site-packages/Utils/Pipeline.py", line 140, in <lambda>
    return reduce(lambda obj, functor: functor(obj), self.funcLine, obj)
  File "/data/srv/HG2111a/sw/slc7_amd64_gcc630/cms/reqmgr2ms/0.5.5.pre3/lib/python3.8/site-packages/Utils/Pipeline.py", line 72, in __call__
    return self.run(obj)
  File "/data/srv/HG2111a/sw/slc7_amd64_gcc630/cms/reqmgr2ms/0.5.5.pre3/lib/python3.8/site-packages/Utils/Pipeline.py", line 75, in run
    return self.func(obj, *self.args, **self.kwargs)
  File "/data/srv/HG2111a/sw/slc7_amd64_gcc630/cms/reqmgr2ms/0.5.5.pre3/lib/python3.8/site-packages/WMCore/MicroService/MSUnmerged/MSUnmerged.py", line 406, in consRecordAge
    isRootFailed = self.rseConsStats[rseName]['root_failed']
KeyError: 'root_failed'
```
diff --git a/src/python/WMCore/MicroService/MSUnmerged/MSUnmerged.py b/src/python/WMCore/MicroService/MSUnmerged/MSUnmerged.py
index 469955859..b82e93c7f 100644
--- a/src/python/WMCore/MicroService/MSUnmerged/MSUnmerged.py
+++ b/src/python/WMCore/MicroService/MSUnmerged/MSUnmerged.py
@@ -403,8 +403,6 @@ class MSUnmerged(MSCore):
 
         isConsDone = self.rseConsStats[rseName]['status'] == 'done'
         isConsNewer = self.rseConsStats[rseName]['end_time'] > self.rseTimestamps[rseName]['prevStartTime']
-        isRootFailed = self.rseConsStats[rseName]['root_failed']
-
         if not isConsNewer:
             msg = "RSE: %s With old consistency record in Rucio Consistency Monitor. " % rseName
             msg += "Skipping it in the current run."
@@ -415,11 +413,6 @@ class MSUnmerged(MSCore):
             msg += "Skipping it in the current run."
             self.logger.warning(msg)
             raise MSUnmergedPlineExit(msg)
-        if isRootFailed:
-            msg = "RSE: %s With failed root in Rucio Consistency Monitor. " % rseName
-            msg += "Skipping it in the current run."
-            self.logger.warning(msg)
-            raise MSUnmergedPlineExit(msg)
 
         return rse
 
['src/python/WMCore/MicroService/MSUnmerged/MSUnmerged.py']