Fix extraction of monitor address.

I don't really understand why this change and the last one to
runzeo.py have their apparent effects, but the tests work and the -m
option to runzeo.py works.

src/ZEO/tests/zeoserver.py

@@ -180,7 +180,7 @@ def main():
     storage = zo.storages[0].open()
     mon_addr = None
     if zo.monitor_address:
-        mon_addr = zo.monitor_address.address
+        mon_addr = zo.monitor_address
     server = StorageServer(
         zo.address,
         {"1": storage},