features/locks: Remove stale entrylk objects from 'blocked_locks' list

* In the event of a DISCONNECT from a client, as part of cleanup,
  entrylk objects are not removed from the blocked_locks list before
  being unref'd and freed, causing the brick process to crash at
  some point when the (now) stale object is accessed again in the list.

* Also during cleanup, it is pointless to try and grant lock to a
  previously blocked entrylk (say L1) as part of releasing another
  conflicting lock (L2), (which is a side-effect of L1 not being
  deleted from blocked_locks list before grant_blocked_entry_locks()
  in cleanup) if L1 is also associated with the DISCONNECTing client.
  This patch fixes the problem.

Change-Id: I3d684c6bafc7e6db89ba68f0a2ed1dcb333791c6
BUG: 1089470
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/7560
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>