Update devstack doc

Add a same local.conf file for freezer devloper.

Change-Id: I556f72efc9541a550855e3617bfeb5cfee92ad30

devstack/README.rst

@@ -32,5 +32,27 @@ Then run devstack normally::
     cd $DEVICE_DIR
     ./stack.sh
 
+This is a sample ``local.conf`` file for freezer developer::
+
+    [[local|localrc]]
+    ADMIN_PASSWORD=stack
+    DATABASE_PASSWORD=stack
+    RABBIT_PASSWORD=stack
+    SERVICE_PASSWORD=$ADMIN_PASSWORD
+
+    DEST=/opt/stack
+    LOGFILE=$DEST/logs/stack.sh.log
+
+    # only install keystone/horizon/swift in devstack
+    # disable_all_services
+    # enable_service key mysql s-proxy s-object s-container s-account horizon
+
+    enable_plugin freezer http://git.openstack.org/openstack/freezer master
+    enable_plugin freezer-api http://git.openstack.org/openstack/freezer-api.git master
+    enable_plugin freezer-tempest-plugin http://git.openstack.org/openstack/freezer-tempest-plugin.git master
+    enable_plugin freezer-web-ui http://git.openstack.org/openstack/freezer-web-ui.git master
+
+    export FREEZER_BACKEND='sqlalchemy'
+
 For more information, see:
- https://docs.openstack.org/devstack/latest/plugins.html
+ https://docs.openstack.org/devstack/latest/index.html