Added pool stat options constants.
Also implemented GetAllPoolStats() function to introduce
the functionality of rbd_pool_stats_option_add_uint64() and rbd_pool_stats_get()
Signed-off-by: Mudit Agarwal <muagarwa@redhat.com>
Add wrapper for rbd_pool_metadata_remove() function which removes pool
metadata associated with a given key.
Signed-off-by: Mudit Agarwal <muagarwa@redhat.com>