vty test: nat_msc_test: setsockopt REUSE to avoid TIME_WAIT problems

When running the testBSCreload test in close succession, I get a "Connection
refused" error because the socket is still in TIME_WAIT state. Passing the
SO_REUSEADDR flag allows reusing the addr despite a TIME_WAIT socket.

Change-Id: I941851b062999ab4b962430f7b27c19935993e0a

openbsc/tests/vty_test_runner.py

@@ -1207,6 +1207,7 @@ def data2str(d):
 
 def nat_msc_test(x, ip, port, verbose = False):
     msc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    msc.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
     msc.settimeout(5)
     msc.bind((ip, port))
     msc.listen(5)