Since https://github.com/canonical/operator/pull/635
harness.update_config()'s behavior has changed and
validates that the config options being set do exist
on the charm.
Change-Id: I2fee2ecb61bf51e7412de74cf1b030114ec3b8dd
Refactor custom status checks to allow the charm specific class and
the inherited general charm type classes to specify status checks.
Change-Id: Ib40fa3b46cc629d5b3e5b199a70cff22451661ee