Peg cassandra to 2.0.*
Peg cassandra to 2.0.*

Change-Id: I4d46a1509f8ef4dc58bac2e0d7d94a5081529da1
Closes-Bug: #1385001

openstack/poppy,obulpathi/poppy,stackforge/poppy,obulpathi/poppy,openstack/poppy,stackforge/poppy,obulpathi/poppy,openstack/poppy,stackforge/poppy