Add a funcutils file for working with functions.

Multiple projects are starting to copy around the various
function utilities that exist in nova and elsewhere. It
would seem appropriate that there exist a helper file in
oslo that was used instead as a central place for this type
of code.

Change-Id: Ia83f26da16b0c868506ecf90e1aaf8affecf3617
Merge "Add a funcutils file for working with functions."