Fix the buildimages jobs: call the ensure-tox role

... and use its output.

tox is not available by default on the images anymore.

Conflicts:
	roles/build-sahara-images-dib/defaults/main.yaml
	roles/build-sahara-images-dib/tasks/main.yaml
	tools/gate/build-images
The backport required some fixes due to the more simplified
structure of the build images role and script in the older
releases.

Change-Id: If5ea0ffdfc51860842c19f0a6f238127d42eb292
(cherry picked from commit 2d0c3a8b98)
(cherry picked from commit 0a9a43cb76)
(cherry picked from commit cdf83a23a0)
(cherry picked from commit 96abd08c28)

playbooks/buildimages/run.yaml

@@ -1,3 +1,4 @@
 - hosts: all
   roles:
+    - ensure-tox
     - build-sahara-images-dib

roles/build-sahara-images-dib/defaults/main.yaml

@@ -2,3 +2,4 @@
 sahara_image_elements_src_dir: "{{ zuul.projects['opendev.org/openstack/sahara-image-elements'].src_dir }}"
 sahara_build_directory: /var/tmp/sahara-image-build
 sahara_plugin: vanilla
+tox_executable: 'tox'

roles/build-sahara-images-dib/tasks/main.yaml

@@ -1,4 +1,4 @@
 - name: Build all the images for the selected plugin
-  command: ./tools/gate/build-images "{{ sahara_plugin }}"
+  command: ./tools/gate/build-images "{{ sahara_plugin }}" "{{ tox_executable }}"
   args:
     chdir: "{{ sahara_image_elements_src_dir }}"

tools/gate/build-images

@@ -1,6 +1,8 @@
 #!/bin/bash -xe
 
 PLUGIN=$1
+TOX_EXECUTABLE=${2:-'tox'}
+
 export DIB_MIN_TMPFS=10
 case "$PLUGIN" in
     "vanilla")
@@ -8,7 +10,7 @@ case "$PLUGIN" in
         for distro in ubuntu centos7; do
             # limit to 2 releases
             for version in 2.7.1 2.8.2; do
-                tox -e venv -- sahara-image-create -x -u -p $PLUGIN -i $distro -v $version
+                ${TOX_EXECUTABLE} -e venv -- sahara-image-create -x -u -p $PLUGIN -i $distro -v $version
             done
         done
         ;;
@@ -20,13 +22,13 @@ case "$PLUGIN" in
             # NOTE(vgridnev): Number of versions are growing; testing only 2 latest
             # releases of CDH
             for version in 5.9 5.11; do
-              tox -e venv -- sahara-image-create -x -u -p $PLUGIN -i $distro -v $version
+              ${TOX_EXECUTABLE} -e venv -- sahara-image-create -x -u -p $PLUGIN -i $distro -v $version
               find . -maxdepth 1 -name '*cloudera*.qcow2' -delete
               sudo rm -rf ~/.cache/image-create
             done
         done
         ;;
     *)
-        tox -e venv -- sahara-image-create -x -u -p $PLUGIN
+        ${TOX_EXECUTABLE} -e venv -- sahara-image-create -x -u -p $PLUGIN
         ;;
 esac