repopick: Don't redirect stdout on --quiet

For some reason, when --quiet is specified (example:
repopick --quiet -c 7834), git ends up in /home instead
of the actual repository.

This is a quick workaround until a proper solution is found

Change-Id: I60e0f684909a23b557ee3147b8954b71be995319
Merge remote-tracking branch 'omni/android-4.4' into omni-4.4