Added task to list tempest tests

tempest list-plugins just lists the installed tempest plugins
discovered by tempest and it does not gurantee that listed
tempest plugins tests are going to get listed/discovered by the
tempest runner.
tempest run -l will list all the tempest tests by checking relative
imports of the listed tests and making sure we are good to run the
tests by using tempest run and helps to avoid import errors during
the running of tempest tests.

Change-Id: Ie1a9266ade6ef0cd411ad0f32ffc3d496d7bde0f

tasks/tempest_post_install.yml

@@ -76,6 +76,20 @@
     executable: /bin/bash
   when: "debug | bool"
 
+- name: List tempest tests
+  shell: |
+    set -e
+    if [ -d {{ tempest_venv_bin }} ];
+    then
+      . {{ tempest_venv_bin }}/activate
+    fi
+    tempest run -l
+  args:
+    chdir: "{{ tempest_workspace }}"
+    executable: /bin/bash
+  when: "debug | bool"
+  changed_when: false
+
 - name: Generate tempest test whitelist
   copy:
     content: |