Fix/privacy levels regex filtering

[DL6ER]

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Fix regex filtering when privacy levels is > 0. This fixes #414

When a new query comes in, we check if we know this domain already.

If so: We check against the regex filters. If one of the filters match, we inject the domain as blocked into our DNS cache.
If not: We continue.

When the same domains is queried another time, we don't evaluate the regex filters any more as we rely on that the query will be quickly replied to from cache.

This usually works fine, however, for a non-zero privacy level, all domains are only stored as hidden in FTL's memory. Accordingly, any subsequent query (after the first )is not validated against the regex filters any more as they all get the same domainID.

This has been fixed.
As a consequence, you cannot lower the privacy level without restarting pihole-FTL!

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