Remove unused code about FREEZER_WEB_UI_DIR in devstack plugin
Remove unused code about FREEZER_WEB_UI_DIR in devstack plugin

Change-Id: I98f0dee1fcf31751c345663886053013b6c8ab0f

openstack/freezer-web-ui,openstack/freezer-web-ui,openstack/freezer-web-ui,openstack/freezer-web-ui