glusterd: hold the lock when submitting ACC in replace-brick

replace-brick handler sets the timer to perform the replace operation and unlocks the big_lock.
So we need to lock inside 'glusterd_do_replace_brick' before submitting the ACC

Change-Id: I5525c62533bd92d3ac46587e5353e2443ad85851
BUG: 1044337
Signed-off-by: Vijaykumar M <vmallika@redhat.com>
Reviewed-on: http://review.gluster.org/6534
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>