check for wfe port liveness in integration tests

We're getting many more spurious "Can't connect to WFE" errors in
TravisCI. So, we add the WFE's main port to the port liveness check in
amqp-integration-test.py.

Fixes #1099

test/startservers.py

@@ -102,7 +102,8 @@ def start(race_detection):
             # If one of the servers has died, quit immediately.
             if not check():
                 return False
-            for debug_port in range(8000, 8005):
+            ports = range(8000, 8005) + [4000]
+            for debug_port in ports:
                 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                 s.connect(('localhost', debug_port))
                 s.close()