Fix port argument parsing

tangostationcontrol/tangostationcontrol/rpc/server.py

@@ -78,11 +78,13 @@ def _create_parser():
     parser.add_argument(
         "--port",
         default=50051,
+        type=int,
         help="HTTP port to listen on.",
     )
     parser.add_argument(
         "--metrics-port",
         default=8001,
+        type=int,
         help="Prometheus metrics HTTP port.",
     )
     parser.add_argument(