(#22358) Interpret */* as anything is accepted

The changes to how we process Accept headers left out the case of being
asked for anything (*/*), which the puppet dashboard will do. This
expands */* to mean the client accepts any format the the requested
endpoint can support.

In addition, this also adds logic to ignore quality specifiers.
Merge pull request #1863 from zaphod42/issue/stable/22358-improper-handling-of-accept-headers

(#22358) Interpret */* as anything is accepted