Use forced_pipeline with timer events

As it stands, if multiple pipelines
have timers with the same timespec, they will all respond to
the events generated for all of them.

Instead of matching on the timespec, associate a timer trigger
with a pipeline directly.

Change-Id: I6a799cc3b59bd7527ace9ee1048bf633dcaa4cd9

zuul/trigger/timer.py

@@ -28,11 +28,12 @@ class Timer(object):
         self.apsched = apscheduler.scheduler.Scheduler()
         self.apsched.start()
 
-    def _onTrigger(self, timespec):
+    def _onTrigger(self, pipeline_name, timespec):
         for project in self.sched.layout.projects.values():
             event = TriggerEvent()
             event.type = 'timer'
             event.timespec = timespec
+            event.forced_pipeline = pipeline_name
             event.project_name = project.name
             self.log.debug("Adding event %s" % event)
             self.sched.addEvent(event)
@@ -78,7 +79,8 @@ class Timer(object):
                                               hour=hour,
                                               minute=minute,
                                               second=second,
-                                              args=(timespec,))
+                                              args=(pipeline.name,
+                                                    timespec,))
 
     def getChange(self, number, patchset, refresh=False):
         raise Exception("Timer trigger does not support changes.")