[CVP-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 is passed to python tests as env var. Then it overrides
partially/fully the options in test config in YAML format.
Added the example in YAML format.

Depends on:
https://gerrit.mcp.mirantis.com/#/c/54895/
https://gerrit.mcp.mirantis.com/#/c/54893/

Change-Id: I419f567f85bedcee04272ec55626e2d8404b35fd
Related-Prod: PROD-29371
diff --git a/jenkins/client/job/validate.yml b/jenkins/client/job/validate.yml
index 0fff778..65e2cd8 100644
--- a/jenkins/client/job/validate.yml
+++ b/jenkins/client/job/validate.yml
@@ -214,7 +214,25 @@
               default: |
                 envs:
                   - tests_set=''
-              description: "YAML context with additional parameters, e.g. skipped_nodes=nal01.local.com,ntw01.local.com or tests_set='tests/test_mtu.py'"
+                override_config:
+                  skipped_nodes: []
+              description: |
+                YAML context with additional parameters. 'envs' key is for environment variables, 'override_config' key is for overriding the global config in YAML format (good for nested parameters). Example:
+                envs:
+                - tests_set='tests/test_mtu.py'
+                override_config:
+                  drivetrain_version: 2019.2.0
+                  skipped_groups:
+                  - log
+                  test_duplicate_ips:
+                    skipped_ifaces:
+                    - lo
+                    - virbr0
+                    - docker_gwbridge
+                    - docker0
+                  test_packages:
+                    skipped_packages: []
+                    skip_test: 'false'
         cvp-func:
           type: workflow-scm
           name: cvp-func