Modify upgrade-* scripts to allow skip configuration if not needed

This allow grenade to move and test from a brand new release to master without
any change.

This way it allows to enable d-g grenade testing new-release->master where for
a just released Openstack means that we don't need any new configuration yet.

Change-Id: I3e685deb61b95116420eae9cacb6b38dc405ffe9
Tempest should be configured with upgrade projects only

This avoid problems try to test projects that are enabled by devstack in the
gate but are not upgraded with grenade.

Change-Id: I7490e88352cdb2afcd3806cc4f62991ae2b43c5c