Filter by roles in Users List page takes upto 20 secs to load with 1000+ users

Two performance issues seen on cluster with 2000 users:

1. Observed that filters by Role like "Ambari Administrator, Cluster User" on Users List pgae - takes between 15-20 seconds to load the page
2. Additionally once a filter is applied, when we apply a second filter to change the number of users displayed on the page from default value of 10 to say 25, that also takes about 15 secs to load