ms_driver: Fix typos after recent refactorings

Change-Id: Id9709743648d60792ec64c97ab1bc6811c4e3e1e
diff --git a/src/osmo_gsm_tester/obj/ms_driver.py b/src/osmo_gsm_tester/obj/ms_driver.py
index c7c1c24..8aecbc8 100644
--- a/src/osmo_gsm_tester/obj/ms_driver.py
+++ b/src/osmo_gsm_tester/obj/ms_driver.py
@@ -67,7 +67,7 @@
         """
 
         # Get the base directory for the virtphy/mobile application
-        inst = util.Dir(os.path.abspath(self._testenv.trial.get_inst('osmocom-bb')))
+        inst = util.Dir(os.path.abspath(self._testenv.suite().trial().get_inst('osmocom-bb')))
 
         # Assume these are dynamically linked and verify there is a lib dir.
         lib = inst.child('lib')