Specify location of 'repo' tool during 'repo init'

This is to prevent 'repo' from failing when kernel.org is down.

BUG=chromium-os:15128
TEST=Ran trybot on empty buildroot and with an existing buildroot that
requires re-initialization.

Integration of changes http://gerrit.chromium.org/gerrit/#change,7111
and http://gerrit.chromium.org/gerrit/#change,7120 from TOT.

Change-Id: Ibafc67bdb0f8244666b1c74516395b57bf79fd52
Reviewed-on: http://gerrit.chromium.org/gerrit/7215
Reviewed-by: Chris Sosa <sosa@chromium.org>
Tested-by: Ryan Cui <rcui@chromium.org>
2 files changed