Ensure shutdown migrations actually time out

Without this a VM that fails to respond to a shutdown will just spin
forever, blocking state changes.

node-daemon/pvcnoded/VMInstance.py

@@ -531,8 +531,20 @@ class VMInstance(object):
             self.zkhandler.write([
                 (('domain.state', self.domuuid), 'shutdown')
             ])
+
+            ticks = 0
             while self.zkhandler.read(('domain.state', self.domuuid)) != 'stop':
+                ticks += 1
+                if ticks > self.config['vm_shutdown_timeout'] * 2:
+                    # We've hit the timeout, forcibly stop the VM and continue
+                    self.zkhandler.write([
+                        (('domain.state', self.domuuid), 'stop')
+                    ])
+                    # Wait 1/2 of a second for the state propagation
+                    time.sleep(0.5)
+                    break
                 time.sleep(0.5)
+
             return True
 
         do_migrate_shutdown = False