ceph::repo integration tests

ceph::repo supports cuttlefish + dumpling on debian. Checking that
apt-cache policy returns the correct version shows the key was properly
installed and matches the repository. Omitting the release parameter
also checks that the default is cuttlefish.

Closes-bug: #1245177

Change-Id: I01ea92798db5d6d74507f247d3e49a93d1f0fc19
Signed-off-by: Loic Dachary <loic@dachary.org>
Merge "ceph::repo integration tests"