Ironic: fetch tempest plugin from git for non-master
Ironic: fetch tempest plugin from git for non-master

The current setup will always use the tempest plugin from the version of
ironic under test. However, we want to always use the master version of
the plugin, so if the change is not proposed against master, fetch
master from git for the tempest plugin.

Change-Id: I9aeb1ac42a85c31115c25cb7fba883da24b45203

openstack-infra/project-config,Tesora/tesora-project-config,dongwenjuan/project-config,openstack-infra/project-config,Tesora/tesora-project-config,dongwenjuan/project-config