Fix unused 'timeout' in OvsdbMonitor start

The 'timeout' parameter needs to be passed to wait_until_true
to make it meaningful and change it to 60 as a default timeout.
In fact 60sec was used till now.

Signed-off-by: Yalei Li <liyl43@chinatelecom.cn>
Change-Id: I2881647e126ab48fa3381543a785ec037866de64

neutron/agent/common/ovsdb_monitor.py

@@ -62,10 +62,10 @@ class OvsdbMonitor(async_process.AsyncProcess):
         self.new_events = {'added': [], 'removed': [], 'modified': []}
         return events
 
-    def start(self, block=False, timeout=5):
+    def start(self, block=False, timeout=60):
         super(OvsdbMonitor, self).start()
         if block:
-            utils.wait_until_true(self.is_active)
+            utils.wait_until_true(self.is_active, timeout=timeout)
 
 
 class SimpleInterfaceMonitor(OvsdbMonitor):