tests: Replace 'suite' with 'tenv'

Change-Id: I777ec59ffd83b861ddc09e85e52d7a8896264b8c
diff --git a/sysmocom/suites/nitb_ussd/assert_extension.py b/sysmocom/suites/nitb_ussd/assert_extension.py
index 8ccab2d..6246e61 100755
--- a/sysmocom/suites/nitb_ussd/assert_extension.py
+++ b/sysmocom/suites/nitb_ussd/assert_extension.py
@@ -3,9 +3,9 @@
 
 USSD_COMMAND_GET_EXTENSION = '*#100#'
 
-nitb = suite.nitb()
-bts = suite.bts()
-ms = suite.modem()
+nitb = tenv.nitb()
+bts = tenv.bts()
+ms = tenv.modem()
 
 print('start nitb and bts...')
 nitb.bts_add(bts)