Make tempest-multinode-full job for stable branch

tempest-multinode-full should be available to run on
all stable branch not just master. All the devstack
changes are backported already.

tempest-multinode-full will use Bionic node from
stein onwards and xenial for all other stable branches.

Change-Id: I94f66028df58a69aa7c26e8a03428bf48596d25c
1 file changed