Check missing config options more reliably
User's config file is not always updated with freshly added config
options in fedpkg release. The reason could be the user's own changes
in the config file prior to the upgrade. It needs user's action
and this fix provides a hint when this problem is detected.
Resolves: rhbz#1813338
JIRA: COMPOSE-4228
Signed-off-by: Ondrej Nosek <onosek@redhat.com>