Using upgrade.old_release in nova.upgrade.pre state

The patch makes the formula use upgrade.old_release while rendering
nova.conf in nova.upgrade.pre state because of the fact that at that
point old release of OpenStack is still installed.

Change-Id: Ifbaa7f37d33091cdb984b0e3d65f323bb457b2df
Related-PROD: PROD-27270 (PROD:27270)
(cherry picked from commit 2bd7c1cfc706b386438ce3fc4e3b25eea5542066)
1 file changed