Patch: In MySQL plugin skip packets that don't contain all mandatory fields

[Michal Kwiatkowski]

Contributed by Jon Foster. Description of the patch by Jon:

> My problem was that with Specter every packet, whether
> or not it was a header packet was being logged to the
> MySQL DB. Because I just want a list of domain names
> this takes up a lot unneeded CPU / disk time and space.
> So the solution I settled on was to make sure that the all
> fields which were "NOT NULL" had valid data before
> sending them to the MySQL server.
>
> I think this same process could be applied to the
> PostgreSQL plugin too but I'm not familiar with PostgreSQL
> C programming and I didn't want to burn anymore time on
> it. I don't even have a PostgreSQL server setup so it would
> be hard to test.
>
> This patch hasn't undergone thorough testing but did
> seem to work for the limited time in which I used it.