Gateway-MT: Re-evaluate logging

[wthorp]

We currently use a global Sync.Once mutex with the Minio logger. The need to copy things between context and use of globals is unfortunate. Could we simplify the logging solution if we use our own middleware? Maybe we would have to implement a custom RegisterAPIRouter equivalent; Bill had one at one point that included all the routes and was hand written, not derived from Minio.

[ferristocrat]

@amwolff @halkyon - is this still relevant?

[halkyon]

@ferristocrat Yes, there is still a need to clean this up by removing the minio logging dependency ("gwlog") in our logging/metrics middleware. This should be labelled as technical debt or whatever label we want to use to describe it to that effect.