config: suites_dir and scenarios_dir are now a list of paths

This allows inheriting suites or scenarios from eg. sysmocom/ dir, while
still allowing to apply new suites and scenarios on top.

Change-Id: Icecdae32d400a6b6da2ebf167c1c795f7a74ae96
diff --git a/sysmocom/ttcn3/main.conf b/sysmocom/ttcn3/main.conf
index 9f38b4e..e4a12d1 100644
--- a/sysmocom/ttcn3/main.conf
+++ b/sysmocom/ttcn3/main.conf
@@ -1,6 +1,6 @@
 state_dir: '/var/tmp/osmo-gsm-tester/state'
-suites_dir: './suites'
-scenarios_dir: './scenarios'
+suites_dir: ['./suites']
+scenarios_dir: ['./scenarios']
 default_suites_conf_path: './default-suites.conf'
 defaults_conf_path: '../defaults.conf'
 resource_conf_path: './resources.conf'