startsync is a no-op, has been for years.  Remove it.

Link: http://tracker.ceph.com/issues/20604Signed-off-by: NYanhu Cao <gmayyyha@gmail.com>
Reviewed-by: N"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>