Swift should have tempurl middleware configured when Ironic is enabled

[Mike Dorman]

Ironic requires that Swift has the tempurl middleware enabled (so that agent-based deploys can download Glance images via unauthenticated temp urls.) However, the proxy-config.conf that's built by kolla-ansible always has that off.

The following content is needed in proxy-config.conf in order to enable it:

[pipeline:main]
pipeline = catch_errors gatekeeper healthcheck cache container_sync bulk ratelimit tempurl authtoken keystoneauth slo dlo proxy-server

[filter:tempurl]
use = egg:swift#tempurl

[filter:authtoken]
delay_auth_decision = True

See: https://docs.openstack.org/newton/config-reference/object-storage/proxy-server.html