suites: Wait for BTS to connect to BSC before continuing

Change-Id: I027e3bfb8f470a811e65e718e2a8c46809fe6396
diff --git a/suites/ussd/assert_extension.py b/suites/ussd/assert_extension.py
index 77e5423..8ccab2d 100755
--- a/suites/ussd/assert_extension.py
+++ b/suites/ussd/assert_extension.py
@@ -11,6 +11,7 @@
 nitb.bts_add(bts)
 nitb.start()
 bts.start()
+wait(nitb.bts_is_connected, bts)
 
 nitb.subscriber_add(ms)