Changes to object store removes SecondaryStorage host from the host
table. This affects the test where we identify the secondary storage nfs
host to login to where we verify if the snapshot is present on the
physical resource.
* added base classes for imagestore/stagingstore operations
* fixed the test to check only if NFS is used as backing store
TODO: Fix for s3 based storage layer
Signed-off-by: Prasanna Santhanam <tsp@apache.org>
(cherry picked from commit 4f973778bf6c2bfc7da2b8c785557e86f81af9d5)