Install openstack services tempest plugin

Since scenarios will start to run tempest, some of them requires
the installation of openstack services tempest plugin. Before, all
the plugins was being installed by default, however the tests being
executed had some conflicts and was decided to not install all at
once, but install only what is required. This patch enables this
behavior.

Change-Id: I9600024b1bd998a15d3aa2629212bdd6591c37d6

roles/validate-tempest/README.md

@@ -30,6 +30,8 @@ Role Variables
 * `tempestmail_config`: config.yaml - name of config file for tempestmail script
 * `tempest_track_resources`: true/false - whether to save the state of resources after tempest run (default: true)
 * `check_tempest_bugs`: true/false - Will check every bugzilla and launchpad bug in the yaml skip file
+* `tempest_plugins`: list - List of openstack services tempest plugins to be
+                     installed
 
 Skip tests file
 ---------------

roles/validate-tempest/defaults/main.yml

@@ -26,6 +26,7 @@ tempest_format: packages # venv or packages
 tempest_whitelist_file_src: "whitelist_file.j2"
 tempest_whitelist_file: "whitelist_file"
 tempest_whitelist: []
+tempest_plugins: []
 skip_file_src: "skip_file.j2"
 skip_file: skip_file
 tempest_until_failure: false

roles/validate-tempest/tasks/pre-tempest.yml

@@ -31,6 +31,12 @@
     mode: 0644
   when: tempest_whitelist|length > 0
 
+- name: Install openstack services tempest plugins
+  yum: state=latest name={{ item }}
+  with_items: "{{ tempest_plugins }}"
+  become: yes
+  when: tempest_plugins|length > 0
+
 - ignore_errors: true
   block:
     - name: Copying bugcheck files