Make git cache delete a defunct directory instead of moving it

Make git cache delete a defunct directory instead of moving it

So the original intention of moving it to a different directory to be deleted later
was to (1) save it for diagnosis (2) be a single inode swap rather than a long
rmtree delete.

1. No one is actually looking at these directories
2. The tmpdir sometimes end up on a different partition, so it ends up being
   a copy + delete instead.  Since we're not getting timeouts from that, its
   probably actually better to just straight up delete it.

BUG=410727
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=291818

[Ryan Tseng, 2014-09-04 10:08:15]

hinoka@google.com changed reviewers:
+ agable@chromium.org, hinoka@google.com, machenbach@chromium.org

[Michael Achenbach, 2014-09-04 10:16:49]

lgtm

[Ryan Tseng, 2014-09-04 10:23:11]

The CQ bit was checked by hinoka@google.com

[commit-bot: I haz the power, 2014-09-04 10:23:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hinoka@chromium.org/538993002/1

[commit-bot: I haz the power, 2014-09-04 10:25:43]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-09-04 10:25:44]

Presubmit check for 538993002-1 failed and returned exit status 1.

Running presubmit commit checks ...
Checking out rietveld...
Running save-description-on-failure.sh
Running push-basic.sh
Running upstream.sh
Running submit-from-new-dir.sh
Running abandon.sh
Running submodule-merge-test.sh
Running upload-local-tracking-branch.sh
Running hooks.sh
Running post-dcommit-hook-test.sh
Running upload-stale.sh
Running patch.sh
Running basic.sh

** Presubmit ERRORS **
Missing LGTM from an OWNER for these files:
    depot_tools/git_cache.py

Pylint (103 files) (29.96s) failed
************* Module
/b/infra_internal/commit_queue/workdir/tools/depot_tools/git_cache.py
W0611: 17,0: Unused import shutil


Presubmit checks took 108.4s to calculate.

Was the presubmit check useful? If not, run "git cl presubmit -v"
to figure out which PRESUBMIT.py was run, then run git blame
on the file to figure out who to ask for help.

[Ryan Tseng, 2014-09-04 13:18:58]

aaron: can you stamp?

[iannucci, 2014-09-04 20:22:46]

iannucci@chromium.org changed reviewers:
+ iannucci@chromium.org

[iannucci, 2014-09-04 20:22:47]

lgtm

[Michael Achenbach, 2014-09-05 10:22:57]

Can this land? I've still trouble with a slave that often runs out of disc space
because of this tmp dir.

[hinoka, 2014-09-05 11:08:00]

The CQ bit was checked by hinoka@chromium.org

[commit-bot: I haz the power, 2014-09-05 11:08:42]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hinoka@chromium.org/538993002/20001

[commit-bot: I haz the power, 2014-09-05 11:10:37]

Committed patchset #2 (id:20001) as 291818