The remove_config() function only removes an exact match for
the configured instance.
This will allow removing plugin configuration when all config is
not known.
Use case: A compute node has been removed, so any host_alive
ping checks that are configured for it should be removed. But at
the time of removal the list of target_hostnames to match are
not known.
Change-Id: I8050e1eed68d7b64f7a968b061afa69fe2e86d72
Story: 2004539
Task: 28287
8d4bd979d5