Log components starts in Zuul.Server

When developping or wondering why Zuul is stuck/having a problem, I
found it very useful to know which tasks it already started.  This patch
adds a logger to the Server() class and log informational message before
most components are started.

Change-Id: I19d0d439c50b42ad6217d92654b9d5e2558d9a7f
diff --git a/zuul/cmd/server.py b/zuul/cmd/server.py
index 7901535..fe5d0fe 100755
--- a/zuul/cmd/server.py
+++ b/zuul/cmd/server.py
@@ -184,6 +184,7 @@
             self.start_gear_server()
 
         self.setup_logging('zuul', 'log_config')
+        self.log = logging.getLogger("zuul.Server")
 
         self.sched = zuul.scheduler.Scheduler()
 
@@ -210,10 +211,13 @@
         self.sched.registerReporter(gerrit_reporter)
         self.sched.registerReporter(smtp_reporter)
 
+        self.log.info('Starting scheduler')
         self.sched.start()
         self.sched.reconfigure(self.config)
         self.sched.resume()
+        self.log.info('Starting Webapp')
         webapp.start()
+        self.log.info('Starting RPC')
         rpc.start()
 
         signal.signal(signal.SIGHUP, self.reconfigure_handler)