Ensure that only the swift-proxy units and swift-storage peers have
access to direct communication with swift storage daemons.
Charm-helpers sync to include ufw module and the ingress_address and
iter_units_for_relation_name functions.
Please review and merge first:
https://github.com/juju/charm-helpers/pull/35
Closes-Bug: #1727463
Change-Id: Id5677edbc40b0b891cbe66867d39d076a94c5436