Tests.yaml was missing a parameter, causing
zaza to pull latest ceph-proxy from charm
store instead of using the changes of
patches proposed in gerrit.

This change fixes it, now zaza deploys
ceph-proxy from local repo created
during tests that contains the patch
proposed in gerrit.

Change-Id: I3681e72f032780b864d02a95cf983f26a0b1c91e