'Failover a single volume.
Attempts to failover a single volume
Sequence:
1. attempt to switch roles from master
2. attempt to change role to master on secondary
returns (success, failure_reason)'

def failover(self, resource, failback):

    LOG.debug('VolumeReplication::failover    %(vol)s', {'vol': resource['name']})
    recovery_mgr = self.get_recovery_mgr()
    remote_recovery_mgr = self.get_remote_recovery_mgr()
    return self._failover_resource(resource, recovery_mgr, remote_recovery_mgr, 'vol', failback)
