Rename ansible_forks to infra_prod_ansible_forks

ansible_forks is a magic var, so when we try to set it ansible
is overriding it.

Change-Id: I3ae45b28d545571f04b02927c3f6c97f145743bc

.zuul.yaml

@@ -1436,7 +1436,7 @@
     semaphore: infra-prod-playbook
     run: playbooks/zuul/run-production-playbook.yaml
     vars:
-      ansible_forks: 5
+      infra_prod_ansible_forks: 5
       infra_prod_playbook_collect_log: false
     nodeset:
       nodes: []
@@ -1487,7 +1487,7 @@
         soft: true
     vars:
       playbook_name: base.yaml
-      ansible_forks: 50
+      infra_prod_ansible_forks: 50
     files:
       - inventory/.*
       - playbooks/host_vars/.*
@@ -1534,7 +1534,7 @@
       - openstack/project-config
     vars:
       playbook_name: manage-projects.yaml
-      ansible_forks: 10
+      infra_prod_ansible_forks: 10
 
 - job:
     name: infra-prod-service-base

playbooks/zuul/run-production-playbook.yaml

@@ -20,11 +20,11 @@
 
       - name: Log a playbook start header
         become: yes
-        shell: 'echo "Running {{ ansible_date_time.iso8601 }}: ansible-playbook -v -f {{ ansible_forks }} /opt/system-config/playbooks/{{ playbook_name }}" > /var/log/ansible/{{ playbook_name }}.log'
+        shell: 'echo "Running {{ ansible_date_time.iso8601 }}: ansible-playbook -v -f {{ infra_prod_ansible_forks }} /opt/system-config/playbooks/{{ playbook_name }}" > /var/log/ansible/{{ playbook_name }}.log'
 
       - name: Run specified playbook on bridge.o.o and redirect output
         become: yes
-        shell: 'ansible-playbook -v -f {{ ansible_forks }} /opt/system-config/playbooks/{{ playbook_name }} >> /var/log/ansible/{{ playbook_name }}.log'
+        shell: 'ansible-playbook -v -f {{ infra_prod_ansible_forks }} /opt/system-config/playbooks/{{ playbook_name }} >> /var/log/ansible/{{ playbook_name }}.log'
 
       always: