Require OsmoMgw in OsmoBsc and update tests

Since Change-Id Ia2882b7ca31a3219c676986e85045fa08a425d7a, osmo-bsc
uses osmo-mgw and utilizes libosmo-mgcp-client to talk to it.

This commit fixes latest constant failures in voice suite.

Change-Id: I1dadd781a357fce33e7bde55e4bcbdaeb4633359
diff --git a/src/osmo_gsm_tester/osmo_bsc.py b/src/osmo_gsm_tester/osmo_bsc.py
index 5fbeea6..736fe8f 100644
--- a/src/osmo_gsm_tester/osmo_bsc.py
+++ b/src/osmo_gsm_tester/osmo_bsc.py
@@ -30,13 +30,15 @@
     process = None
     bts = None
     encryption = None
+    mgw = None
 
-    def __init__(self, suite_run, msc, ip_address):
+    def __init__(self, suite_run, msc, mgw, ip_address):
         super().__init__(log.C_RUN, 'osmo-bsc_%s' % ip_address.get('addr'))
         self.suite_run = suite_run
         self.ip_address = ip_address
         self.bts = []
         self.msc = msc
+        self.mgw = mgw
 
     def start(self):
         self.log('Starting osmo-bsc')
@@ -73,6 +75,7 @@
         values = dict(bsc=config.get_defaults('bsc'))
         config.overlay(values, self.suite_run.config())
         config.overlay(values, dict(bsc=dict(ip_address=self.ip_address)))
+        config.overlay(values, self.mgw.conf_for_client())
 
         bts_list = []
         for bts in self.bts: