rbd: add rbd_obj_watch_request_helper() helper
rbd: add rbd_obj_watch_request_helper() helper

In the past, rbd_dev_header_watch_sync() used to handle both watch and
unwatch requests and was entangled and leaky.  Commit b30a01f2a307
("rbd: fix osd_request memory leak in __rbd_dev_header_watch_sync()")
split it into two separate functions.  This commit cleanly abstracts
the common bits, relying on the fixed rbd_obj_request_wait().

Signed-off-by: Ilya Dryomov <33f1a10eef0a3354755a1541edfdb100ff87fcfc@inktank.com>
Reviewed-by: Alex Elder <f429030cf5c0faf36fac3d102073b6e63a647baa@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs