Add 'backup' status for contrail.
Add 'backup' status for contrail.

If more than one instance is running,
the service has only one active instance
and the other instances are backup.

Change-Id: I575ccb754eb4675e4ea1e4d46f803bfdf75392fc

stackforge/fuel-plugin-contrail,stackforge/fuel-plugin-contrail,stackforge/fuel-plugin-contrail,stackforge/fuel-plugin-contrail