tests: Replace 'suite' with 'tenv'

Change-Id: I777ec59ffd83b861ddc09e85e52d7a8896264b8c
diff --git a/sysmocom/suites/voice/mo_mt_call_osmux.py b/sysmocom/suites/voice/mo_mt_call_osmux.py
index acf7d71..c65caab 100755
--- a/sysmocom/suites/voice/mo_mt_call_osmux.py
+++ b/sysmocom/suites/voice/mo_mt_call_osmux.py
@@ -2,7 +2,7 @@
 from osmo_gsm_tester.testenv import *
 
 import testlib
-suite.test_import_modules_register_for_cleanup(testlib)
+tenv.test_import_modules_register_for_cleanup(testlib)
 from testlib import test_mo_mt_call
 
 test_mo_mt_call(True, True)