Update fixtures.py to use "127.0.0.1" for local ports (#2384)

Author: wbarnha

test/fixtures.py

@@ -25,7 +25,7 @@
 
 def get_open_port():
     sock = socket.socket()
-    sock.bind(("", 0))
+    sock.bind(("127.0.0.1", 0))
     port = sock.getsockname()[1]
     sock.close()
     return port