remus: fix check for installed qdiscs on ifb

current check includes ingress and pfifo_fast.
Add mq to the list of allowed qdiscs already installed
on ifb. This patch fixes cases where remus fails to start,
due to an mq qdisc already present on the vif.

Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

xen-unstable changeset: 23109:c8ae80a11d47
Backport-requested: Shriram Rajagopalan <rshriram@gmail.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/python/xen/remus/device.py

@@ -320,9 +320,9 @@ class BufferedNIC(CheckpointedDevice):
             if q['kind'] == 'plug':
                 self.installed = True
                 return
-            if q['kind'] not in ('ingress', 'pfifo_fast'):
+            if q['kind'] not in ('ingress', 'pfifo_fast', 'mq'):
                 raise BufferedNICException('there is already a queueing '
-                                           'discipline on %s' % devname)
+                                           'discipline %s on %s' % (q['kind'], devname))
 
         print ('installing buffer on %s... ' % devname),
         req = qdisc.addrequest(self.bufdevno, self.handle, self.q)