On Master restart all servers are assigned to default rsgroup.

Steps to reproduce:

1. Install a HBase cluster with three RS(rs1,rs2 and rs3) and one Master
2. Create two rsgroups r1 and r2 and move rs1 to r1 and rs2 to r2

   add_rsgroup 'r1';add_rsgroup 'r2';move_servers_rsgroup 'r1',['host1:16020'];move_servers_rsgroup 'r2',['host2:16020']
   

3. Restart Master
4. Run list_rsgroups for hbase shell, all region servers are assigned to default regroup.