[Sanity] Override nested params of global config in Jenkins

* Added possibility to overwrite the nested parameters (dictionaries)
in Jenkins. Jenkins EXTRA_PARAMS will have the "override_config"
key which can override partially/fully all options in global
config in YAML format.
* global_config.yaml has now YAML format with lists started with dash

Depends on:
https://gerrit.mcp.mirantis.com/#/c/54895/
https://gerrit.mcp.mirantis.com/#/c/54897/

Change-Id: I8a122cd4307fd6ea341d92fa25f5324ac8eb9f08
Related-Prod: #PROD-29371
diff --git a/test_set/cvp-sanity/tests/test_packet_checker.py b/test_set/cvp-sanity/tests/test_packet_checker.py
index c132294..40c7bd7 100644
--- a/test_set/cvp-sanity/tests/test_packet_checker.py
+++ b/test_set/cvp-sanity/tests/test_packet_checker.py
@@ -93,7 +93,7 @@
 def test_packages_are_latest(local_salt_client, nodes_in_group):
     config = utils.get_configuration()
     skip = config.get("test_packages")["skip_test"]
-    if skip:
+    if skip.lower() == 'true':
         pytest.skip("Test for the latest packages is disabled")
     skipped_pkg = config.get("test_packages")["skipped_packages"]
     group, nodes = nodes_in_group