Use overcloud_templates_path variable defines in extras-common

overcloud_templates_path is defined in roles/extras-common.
Change Id216cf2091e23221cb5ae54421e3051dce1a6d18 redefines this
variable diffrently in the overcloud-prep-config role, which causes
the baremetal deploys using bonds to fail.

The review removes the variable default in overcloud-prep-config.
The role README.md is updated to refer to the extras-common default.

Change-Id: I149d47f31a5fb87d700e25d1743e11f06422e9a6

roles/overcloud-prep-config/README.md

@@ -16,8 +16,7 @@ Role Variables
 **Note:** Make sure to include all environment file and options from your
 [initial Overcloud creation](https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/7/html/Director_Installation_and_Usage/sect-Scaling_the_Overcloud.html).
 
-- `working_dir`: <'/home/stack'> -- working directory for the role. Assumes
-  stackrc file is present at this location
+- `working_dir`: <'/home/{{ undercloud_user }}'> -- defined in roles/extras-common
 - `baremetal_instackenv`: <"{{ working_dir }}/instackenv.json"> -- location of
   instackenv.json to copy over
 - `baremetal_network_environment`: <"{{ working_dir }}/network-isolation.yml">
@@ -32,6 +31,8 @@ Role Variables
 - `download_overcloud_templates_rpm`: if set to true, allow the user to
   download a tripleo-heat-templates rpm package from a url defined by the
   variable `tht_rpm_url`
+- `overcloud_templates_path`: <'/usr/share/openstack-tripleo-heat-templates'> --
+  defined in roles/extras-common
 
 [1] Names are derived from the `tripleo-heat-templates configuration <https://github.com/openstack/tripleo-heat-templates/tree/master/network/config>`_
 

roles/overcloud-prep-config/defaults/main.yml

@@ -37,4 +37,3 @@ bond_with_vlans_copy_nic_configs_script: bond-with-vlans-copy-nic-configs.sh.j2
 bond_with_vlans_nic_configs_log: bond_with_vlans_nic_configs_script_log
 
 tht_rpm_url: https://trunk.rdoproject.org/centos7-{{ release }}/current/
-overcloud_templates_path: "{{ working_dir }}/tripleo-heat-templates"