Fix horizon-nodejs jobs

Tox is not anymore pre-installed on the OpenDev CI images.
The file package.json needs tox, install it to fix the job.

Install it via a pre-run playbook so that this is run in addition to all
of the playbooks of the parent.

Note for the reviewer in stable/stein we run nodejs-4 jobs as runtime.
I have cherry-pick this change from master which run nodejs-10 job
but simliar changes fixes the nodejs-4 jobs So I have added pre-run
playbook for nodejs-4 job as well.

Change-Id: Icf82fa96f7d90453f78cf564c847682a286ed575
(cherry picked from commit 7cd0debebe)

.zuul.yaml

@@ -102,6 +102,7 @@
     vars:
       node_version: 4
     nodeset: ubuntu-xenial
+    pre-run: playbooks/horizon-nodejs/pre.yaml
     required-projects:
       openstack/horizon
 
@@ -113,6 +114,7 @@
     vars:
       node_version: 4
     nodeset: ubuntu-xenial
+    pre-run: playbooks/horizon-nodejs/pre.yaml
     required-projects:
       openstack/horizon
 
@@ -124,6 +126,7 @@
     vars:
       node_version: 10
     nodeset: ubuntu-bionic
+    pre-run: playbooks/horizon-nodejs/pre.yaml
     required-projects:
       openstack/horizon
 
@@ -135,6 +138,7 @@
     vars:
       node_version: 10
     nodeset: ubuntu-bionic
+    pre-run: playbooks/horizon-nodejs/pre.yaml
     required-projects:
       openstack/horizon
 

playbooks/horizon-nodejs/pre.yaml

@@ -0,0 +1,6 @@
+- hosts: all
+  roles:
+    # package.json needs to run 'tox' as command, ensure that it's
+    # installed and can be used globally.
+    - role: ensure-tox
+      ensure_global_symlinks: True