Resource manager should not check replication status if all replication has the same priority

Resource manager will:

1. Check replication status
2. Check replication priorities
3. Compute the necessary actions based on priority

When all replications have the same priority, there will be no throttling action and step 1 above may be unnecessary especially when it adds to contention with ns_server's goxdcr_stats_collector and causes dropped ticks when there is a large number of replications.