Remove use of role_name variable

`role_name` is a reserved variable name. Instead, use the explicit
service_role_name variables when adding roles to users.

Change-Id: Ia5fa0e400aeec6d808891c5dd793ee8177d9b5f3

tasks/neutron_service_add.yml

@@ -60,7 +60,7 @@
     endpoint: "{{ keystone_service_adminurl }}"
     user_name: "{{ service_user_name }}"
     tenant_name: "{{ service_tenant_name }}"
-    role_name: "{{ role_name }}"
+    role_name: "{{ neutron_service_role_name }}"
     insecure: "{{ keystone_service_adminuri_insecure }}"
   register: add_service
   when: not neutron_service_in_ldap | bool

tasks/neutron_service_setup.yml

@@ -25,6 +25,5 @@
     service_publicurl: "{{ neutron_service_publicurl }}"
     service_internalurl: "{{ neutron_service_internalurl }}"
     service_adminurl: "{{ neutron_service_adminurl }}"
-    role_name: "{{ neutron_service_role_name }}"
   tags:
     - neutron-server