in-tree: Add check for empty secret/context on create/delete
in-tree: Add check for empty secret/context on create/delete

Signed-off-by: Grant Griffiths <7561d7b6fa252e14d948ef730f22c68c9d861f6b@portworx.com>

libopenstorage/openstorage,libopenstorage/openstorage,libopenstorage/openstorage