The init method is a stub for handling new pool initialization. It
currently only handles setting the application tag. The stats method
will quickly calculate the number of images and provisioned space for
those images within the pool. Querying the pool stats on a pool with
10,000 images only required approximately 2 seconds as compared to
over 2 minutes for a "rbd ls -l" scan.
Signed-off-by: Jason Dillaman <dillaman@redhat.com>