This was originally fixed in commit 7578326 but this caused problems. It
was subsequently reverted in commit 6d2e9ee.
This change uses a common DHCPAgentContext and takes care to check for a
pre-existing setting in the dhcp_agent.ini. Only allowing a config
change if there is no pre-existing setting.
Please review and merge charm-helpers PR:
https://github.com/juju/charm-helpers/pull/422
Partial-Bug: #1831935
func-test-pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/157
Change-Id: I4848a3246d3450540acb8d2f479dfa2e7767be60
4075af6a11