rbd: Validate splitting volume name
rbd: Validate splitting volume name

We split the name field in the connection info to get the pool and
image.  Make sure splitting on '/' yields two components.

Signed-off-by: Adam Litke <ed9d9846a37e30d0259dba27fda9320ea24a6102@redhat.com>

kubernetes-incubator/external-storage,humblec/external-storage,humblec/external-storage,childsb/external-storage,humblec/external-storage,kubernetes-incubator/external-storage,childsb/external-storage,kubernetes-incubator/external-storage,childsb/external-storage