osmo-gsm-tester.py: Fix import error when using default-suites.conf

Recent commit refactoring stuff introduced an import error only
triggered when default-suites.conf is used (no -s param).
This commit fixes the issue.

Fixes: ea8c3d4b1235ef703e54cd963bc96f6716168387
Change-Id: I1534cfba55c69ed5c1354175f8b5df9b656b7d82
diff --git a/src/osmo-gsm-tester.py b/src/osmo-gsm-tester.py
index dc1e058..7bd2fd6 100755
--- a/src/osmo-gsm-tester.py
+++ b/src/osmo-gsm-tester.py
@@ -73,7 +73,7 @@
 from osmo_gsm_tester.core import log
 from osmo_gsm_tester.core import trial
 from osmo_gsm_tester.core import suite
-from osmo_gsm_tester.core.config import read_config_file, DEFAULT_SUITES_CONF
+from osmo_gsm_tester.core import config
 from osmo_gsm_tester.core.schema import generate_schemas
 
 def sig_handler_cleanup(signum, frame):