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/suites/aoip_ussd/assert_extension.py b/suites/aoip_ussd/assert_extension.py
index 5e934db..36d6222 100755
--- a/suites/aoip_ussd/assert_extension.py
+++ b/suites/aoip_ussd/assert_extension.py
@@ -6,8 +6,9 @@
 hlr = suite.hlr()
 bts = suite.bts()
 mgcpgw = suite.mgcpgw(bts_ip=bts.remote_addr())
+mgw_bsc = suite.mgw()
 msc = suite.msc(hlr, mgcpgw)
-bsc = suite.bsc(msc)
+bsc = suite.bsc(msc, mgw_bsc)
 stp = suite.stp()
 ms = suite.modem()
 
@@ -15,6 +16,7 @@
 stp.start()
 msc.start()
 mgcpgw.start()
+mgw_bsc.start()
 
 bsc.bts_add(bts)
 bsc.start()