glusterd: release big locks while doing mount

Else things can deadlock in getspec v/s glusterd_do_mount()

Change-Id: Ie70b43916e495c1c8f93e4ed0836c2fb7b0e1f1d
BUG: 997576
Signed-off-by: Anand Avati <avati@redhat.com>
Reviewed-on: http://review.gluster.org/5636
Tested-by: Joe Julian <joe@julianfamily.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>