Change default datasource from influx to prometheus

Change-Id: I8e9ce24d0c92ed646c782841de09301a7fef35b5
diff --git a/tcp_tests/templates/cookied-bm-contrail40/salt-context-cookiecutter-contrail.yaml b/tcp_tests/templates/cookied-bm-contrail40/salt-context-cookiecutter-contrail.yaml
index 85182a6..1125a8f 100644
--- a/tcp_tests/templates/cookied-bm-contrail40/salt-context-cookiecutter-contrail.yaml
+++ b/tcp_tests/templates/cookied-bm-contrail40/salt-context-cookiecutter-contrail.yaml
@@ -217,7 +217,7 @@
   stacklight_log_node02_hostname: log02
   stacklight_log_node03_address: 10.167.8.63
   stacklight_log_node03_hostname: log03
-  stacklight_long_term_storage_type: influxdb
+  stacklight_long_term_storage_type: prometheus
   stacklight_monitor_address: 10.167.8.70
   stacklight_monitor_hostname: mon
   stacklight_monitor_node01_address: 10.167.8.71