cerbero: Fix circular imports in shell.py
cerbero: Fix circular imports in shell.py

Import cerbero.hacks inside the function call that needs it to avoid
a top-level circular dependency in the importing. This is not
a problem right now, but it's a ticking time-bomb.

GStreamer/cerbero,GStreamer/cerbero,atsushieno/cerbero,nirbheek/cerbero,atsushieno/cerbero,atsushieno/cerbero,nirbheek/cerbero,atsushieno/cerbero,atsushieno/cerbero,GStreamer/cerbero,nirbheek/cerbero,GStreamer/cerbero,GStreamer/cerbero,nirbheek/cerbero