mgmt/glusterd: Update sub_count on remove brick

Change-Id: I7c17de39da03c6b2764790581e097936da406695
BUG: 1002556
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/5902
Tested-by: Gluster Build System <jenkins@build.gluster.com>