This reverts commit 5908f990.

Reason for revert:
Introduces bugs when deleting files.
The reason is that 
  patchlevel = patchlevel or self.patchlevel
will evaluate to self.patchlevel also when patchlevel is 0, which is wrong.

Original change's description:
> Fix checkout.py issues when p.patchlevel > 1.
> 
> When p.patchlevel > 1, p.filename does not correspond to the files that
> git-apply would modify.
> 
> See bug for details
> 
> Bug: 764294
> Change-Id: Icdb803056e306edb25238b2d9cdabd3ff175d8ed
> Reviewed-on: https://chromium-review.googlesource.com/663357
> Reviewed-by: Aaron Gable <agable@chromium.org>
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

TBR=kjellander@chromium.org,agable@chromium.org,ehmaldonado@chromium.org

Change-Id: Ifa1f94602a023228cb32e5fe3fa07586b466981a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 764294
Reviewed-on: https://chromium-review.googlesource.com/663266Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>