/openrtb2/video endpoint panics due to uninitialized TCF2Config

[scr-oath]

A recent change in #3639 causes the /openrtb2/video endpoint to panic because, seemingly, only auction + amp_auction initialize the field which is used without a nil check:

https://github.com/prebid/prebid-server/pull/3639/files#r1622769615

Any post to the video endpoint causes this nil-pointer panic.

I'm surprised no unit tests tickled this, but it should be pretty easy to make one and see the panic straight away.

[thomasvng]

working on a fix!