Update to latest hacking

We need to quickly update global requirements to
unblock the gate to get this fix in 0.9.4 of
hacking
 I4b42d081965b6d898b178cbe9232b47cfed17d8a

Without this fix, the new oslo concurrency shim
is not detected as a module and flake8 fails.

Change-Id: Ia1c90a0b13ee2ab79be71c71990cb2b86f44b127