Add the variable list_skipped_job

The list_skipped role have a variable called list_skipped_job.
This variable makes the role filter the list of tests to be
skipped per job. This makes required in order to start use
the tempest-skiplist to skip tests for specific jobs (for
example component-pipeline jobs).
Without passing this variable, we are not able to filter
tempest tests per job.

Depends-On: https://review.opendev.org/#/c/751828/
Change-Id: I640b4efc9474614b44cbcf56d52736760dffc230

playbooks/tempest.yml

@@ -5,6 +5,7 @@
     - name: Load tests to be skipped
       vars:
         list_skipped_release: "{{ release }}"
+        list_skipped_job: "{{ zuul.job | default(omit) }}"
       include_role:
         name: list_skipped