Apply workaround for PasteDeploy only on stable/queens
Apply workaround for PasteDeploy only on stable/queens

The workaround in order to fix the issue with Paste/PasteDeploy being
pulled in as system packages when installing ceph is only needed for the
Pike UCA. Assume that we only use that when devstack is running at the
stable/queens branch.

Change-Id: I0bbf04be015b777b3feb2c5e837b1f46f81cf3e9

openstack/devstack-plugin-ceph