This reverts commit 1123fea2.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> [git_bootstrap.py] Remove unused options, use cipd in %PATH%.
> 
> In particular:
>   * Rely on cipd.bat in %PATH%
>   * Always calculate --bits
>   * Rely on %CIPD_CACHE_DIR%
> 
> R=​vadimsh@chromium.org
> 
> Bug: 635421
> Change-Id: I972edfd7f48e90770696afba70ec7e11fc24ce95
> Reviewed-on: https://chromium-review.googlesource.com/495407
> Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
> Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
> 

TBR=iannucci@chromium.org,vadimsh@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I3536d6668432141ae1528ca49ea66d97fdeb5318
Reviewed-on: https://chromium-review.googlesource.com/495727Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>