Use keystone session with heatclient in integration tests

Change-Id: I4c66927e3dd3e1a91cfab94f26a24dbe8932bde8
Related-Bug: #1695144
(cherry picked from commit ff3fbd546715ef21a2b31862f36a3e8d05e0d0e1)
Partial-Issue: PROD-20603
1 file changed