BUGFIX: MS_cache: fetch_from_api() & is_website_whitelisted()
BUGFIX: MS_cache: fetch_from_api() & is_website_whitelisted()

Bug: params.update() is an in-place change without return value
Bug: MetasmokeCache.fetch_from_api returns a tuple, not a single value.
Improve: Have the cache optionally store a list of strings,
created from a single property, rather than a list of dicts, so we
don't have to convert to a list of strings every time this is called
in order to use `domain.lower() in whitelist`.

Charcoal-SE/SmokeDetector,Charcoal-SE/SmokeDetector