suites: Wait for BTS to connect to BSC before continuing

Change-Id: I027e3bfb8f470a811e65e718e2a8c46809fe6396
diff --git a/suites/aoip_ussd/assert_extension.py b/suites/aoip_ussd/assert_extension.py
index 181f07f..5969b01 100755
--- a/suites/aoip_ussd/assert_extension.py
+++ b/suites/aoip_ussd/assert_extension.py
@@ -22,6 +22,7 @@
 bsc.start()
 
 bts.start()
+wait(bsc.bts_is_connected, bts)
 
 hlr.subscriber_add(ms)