There were multiple problems with the setting and usage of
hide_unsupported_rhel_options. Due to the fact that the option has
several diferent namings throughout the code, this patch is renaming
it to stable_defaults, which basically says what the option does and
makes it possible to use it without need for more than one negation
(where the old code had up to 4 of them in some places), which also
helps understanding it.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>