Added/checked template tests

Added inline stubs for endpoint, db_uri, rabbit_servers and
get_password.
In spec/cinder_common_spec.rb, the most complex template, there is a
context for commonly named attributes, those which name matches a
node attribute with keys ['openstack']['block-storage'][attr_key],
storage_availability_zone for instance. This pattern is used in lots
of configuration spec blocks, for example in
['openstack']['block-storage']['vmware'][attr_key].
I've also found what appear to be some incongruences, like duplicated
conditional checks for volume driver types and repeated storwize
settings at the bottom. Perhaps these should be checked in another
bug.
Custom template banners have been added when needed.

Change-Id: I4e90a602caea044d5415ca9b637d19d82f9ab227
Closes-Bug: #1304412