This reverts commit 70f351e7.

Reason for revert: CIPD bootstrap is now PS 2.0 compatible.

BUG=674363,673940

Original change's description:
> Revert "Stop adhoc cipd client bootstrap."
> 
> This reverts commit c6569aab.
> 
> Reason for revert: This caused crbug.com/674363, needs further investigation.
> 
> Original change's description:
> > Stop adhoc cipd client bootstrap.
> > 
> > This was used before to get the git installer, but now depot_tools manages its
> > own copy of CIPD.
> > 
> > BUG=673940
> > 
> > Change-Id: I1077ff7eb27d9ca191dc0092b7cacaaa69c40449
> > Reviewed-on: https://chromium-review.googlesource.com/420303
> > Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
> > Reviewed-by: Aaron Gable <agable@chromium.org>
> > Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
> > 
> 
> TBR=iannucci@chromium.org,agable@chromium.org,vadimsh@chromium.org,dnj@chromium.org,sebmarchand@chromium.org,chromium-reviews@chromium.org
> BUG=673940
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> 
> Change-Id: I7aa5561ad0df67831987cd8d53a84105d42d9663
> Reviewed-on: https://chromium-review.googlesource.com/420320
> Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
> Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
> 

TBR=iannucci@chromium.org,agable@chromium.org,vadimsh@chromium.org,dnj@chromium.org,chromium-reviews@chromium.org,sebmarchand@chromium.org
BUG=673940
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I822312b1507003ee07930ef7527e12b997457673
Reviewed-on: https://chromium-review.googlesource.com/420321
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>