linux-phytec-ti

rbd: rbd_dev_header_unwatch_sync() variant

Introduce __rbd_dev_header_unwatch_sync(), which doesn't flush notify
callbacks.  This is for the new rados_watcherrcb_t, which would be
called from a notify callback.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>