aoip: add osmo-stp, now required for aoip runs

Change-Id: I35d4cb0d173eec240bccc1f3a5965a774b7b3506
diff --git a/src/osmo_gsm_tester/suite.py b/src/osmo_gsm_tester/suite.py
index eeaf7df..be799d3 100644
--- a/src/osmo_gsm_tester/suite.py
+++ b/src/osmo_gsm_tester/suite.py
@@ -25,7 +25,7 @@
 import pprint
 from . import config, log, template, util, resource, schema, ofono_client, event_loop
 from . import osmo_nitb
-from . import osmo_hlr, osmo_mgcpgw, osmo_msc, osmo_bsc
+from . import osmo_hlr, osmo_mgcpgw, osmo_msc, osmo_bsc, osmo_stp
 from . import test
 
 class Timeout(Exception):
@@ -322,6 +322,11 @@
             ip_address = self.ip_address()
         return osmo_bsc.OsmoBsc(self, msc, ip_address)
 
+    def stp(self, ip_address=None):
+        if ip_address is None:
+            ip_address = self.ip_address()
+        return osmo_stp.OsmoStp(self, ip_address)
+
     def bts(self, specifics=None):
         return bts_obj(self, self.reserved_resources.get(resource.R_BTS, specifics=specifics))