charm config state must not be processed on every event

[Dmitrii Shcherbakov]

While pad.lv/1712972 fixed the original issue I think it's better to avoid calling a handler on every invocation altogether.

[Dmitrii Shcherbakov (dmitriis)]

https://review.openstack.org/#/c/531562/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/531562
Committed: https://git.openstack.org/cgit/openstack/charm-keystone-ldap/commit/?id=b5fe0ef6c9a999cf5f622de6a6bd0727ccf5459c
Submitter: Zuul
Branch: master

commit b5fe0ef6c9a999cf5f622de6a6bd0727ccf5459c
Author: Dmitrii Shcherbakov <email address hidden>
Date: Sat Jan 6 19:37:57 2018 +0300

    refactor keystone-ldap

    * replace singletons with provide_charm_instance (in the code and tests)
    * select an openstack release based on keystone package due to the lack
    of openstack-origin from the principal layer (this is a subordinate, see
    https://git.io/vNTyx)
    * use reactive triggers to drop config.complete (new configuration
    completeness) and config.rendered (non-stale config is rendered) on
    config.changed
    * do not check config completeness on every event - only when config has
    actually changed
    * remove the domain configuration file when relation with keystone is
    removed (service restart should be performed on the keystone charm side)
    * replace path_hash with file_hash (path_hash returns a new dict)
    * modify unit tests to reflect the changes

    Change-Id: Ied4b6ed64354e3de3c78e6ac809666ee9ae29d1a
    Closes-Bug: #1741661