Enable snapshot deletion with deps on ceph

This is not be a problem anymore with newer ceph
and devstack-plugin-ceph has been setting the minimum
client version to mimic (which enables the required features)
for a while.
So use the new variable which references volume/image
dependencies but it is really about volume dependencies.

Change-Id: I673497466b0fb6f7954aebe05ee6d1bd24e78769
2 files changed