rbd: define rbd_dev_{create,destroy}() helpers
rbd: define rbd_dev_{create,destroy}() helpers

Encapsulate the creation/initialization and destruction of rbd
device structures.  The rbd_client and the rbd_spec structures
provided on creation hold references whose ownership is transferred
to the new rbd_device structure.

Signed-off-by: Alex Elder <f429030cf5c0faf36fac3d102073b6e63a647baa@inktank.com>
Reviewed-by: Josh Durgin <51652c783f70f5b272ebd02f1fd20d3af7a2449f@inktank.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs