Backport HBASE-18350 (fix RSGroups) to branch-1 (Only port the part fixing table locking issue.)

When working on HBASE-20666, I found out HBASE-18350 did not get ported to branch-1, which causes procedure to hang when #moveTables called sometimes. 

After looking into the 18350 patch, seems it's important since it fixes 4 issues. This Jira is an attempt to backport it to branch-1.

Edited: Aug26.

After reviewed the HBASE-18350 patch. I decided to only port part 2 of the patch.

Because part1 and part3 is AMv2 related. I won't touch is since Amv2 is only for branch-2

 

Subject: [PATCH] HBASE-18350 RSGroups are broken under AMv2

• Table moving to RSG was buggy, because it left the table unassigned.
    Now it is fixed we immediately assign to an appropriate RS
    (MoveRegionProcedure).
  • Table was locked while moving, but unassign operation hung, because*
      locked table queues are not scheduled while locked. Fixed.   ---- port this one.
• ProcedureSyncWait was buggy, because it searched the procId in
    executor, but executor does not store the return values of internal
    operations (they are stored, but immediately removed by the cleaner).
• list_rsgroups in the shell show also the assigned tables and servers.