Change default controller for mn to ovsc (ovs-controller.)

Also add check to see if another controller is running -
eventually we should really detect errors from starting the
controller!!

bin/mn

@@ -48,7 +48,7 @@ HOSTS = { 'proc': Host,
           'rt': custom( CPULimitedHost, sched='rt' ),
           'cfs': custom( CPULimitedHost, sched='cfs' ) }
 
-CONTROLLERDEF = 'ref'
+CONTROLLERDEF = 'ovsc'
 CONTROLLERS = { 'ref': Controller,
                 'ovsc': OVSController,
                 'nox': NOX,