Removing entries from whitelist file does not remove them from the in-memory whitelist

[GilHoggarth]

Seems like the code to read the whitelist of urls to allow to be shown correctly reads new urls but fails to remove urls that have previously been added (i.e., attempting to reverse a whitelist allowance).
Presumably, though this wasn't tested, restarting wayback would solve this but such an action should not be required.