Added possibility to deploy Drivetrain separately from other services

Change-Id: I0deab9a27fd8fbd3e2c6e4b726a387513f9574c1
diff --git a/tcp_tests/helpers/ext.py b/tcp_tests/helpers/ext.py
index 804d110..8dbf832 100644
--- a/tcp_tests/helpers/ext.py
+++ b/tcp_tests/helpers/ext.py
@@ -45,6 +45,7 @@
     'salt_deployed',
     'common_services_deployed',
     'oss_deployed',
+    'drivetrain_deployed'
     'openstack_deployed',
     'sl_deployed',
     'virtlet_deployed',