throttler releases less requests than the available quota
Motivation
----------
```
conveyor-throttler[8b7233a:0/4]: limit to UKI-NORTHGRID-LANCS-HEP-CEPH_DATADISK activity Data rebalancing: can release 41853 out of 1628126 waiting requests. Account share:
 {ddmadmin: {'waiting': 1627436, 'active': 42723, 'residual_capacity': 0}, panda: {'waiting': 690, 'active': 15424, 'residual_capacity': 690}}
```
this is due to the code which splits the quota per account to achieve fair share


diff --git a/lib/rucio/daemons/conveyor/throttler.py b/lib/rucio/daemons/conveyor/throttler.py
index 9dcd805b8..7e99f88a0 100644
--- a/lib/rucio/daemons/conveyor/throttler.py
+++ b/lib/rucio/daemons/conveyor/throttler.py
@@ -334,17 +334,11 @@ def _split_threshold_per_account(per_account_stats, total_to_release):
     nr_accounts = len(per_account_stats)
     remaining_to_release = total_to_release
     remaining_accounts = nr_accounts
-    for account, account_stat in sorted(per_account_stats.items(), key=lambda i: i[1]['active']):
+    for account, account_stat in sorted(per_account_stats.items(), key=lambda i: i[1]['waiting']):
         threshold_per_account = math.ceil(remaining_to_release / remaining_accounts)
 
         waiting = account_stat['waiting']
-        active = account_stat['active']
-        if active > threshold_per_account:
-            to_release_for_account = 0
-        elif active + waiting <= threshold_per_account:
-            to_release_for_account = waiting
-        else:
-            to_release_for_account = threshold_per_account - active
+        to_release_for_account = min(waiting, threshold_per_account)
 
         yield account, to_release_for_account
 
['lib/rucio/daemons/conveyor/throttler.py']