Do not override CHROME_DEVEL_SANDBOX in tools/valgrind/valgrind_test.py

Do not override CHROME_DEVEL_SANDBOX in tools/valgrind/valgrind_test.py

Setting that variable to an empty string is not a supported way of disabling the
sandbox. tools/valgrind/chrome_tests.py is supposed to pass "--no-sandbox" which
takes care of that.

BUG=245376
TBR=jln@chromium.org, timurrrr@chromium.org
NOTRY=true

Committed: https://crrev.com/65f9d720f95b3c6f8465ad2fe7d49ac098b51a31
Cr-Commit-Position: refs/heads/master@{#313517}

[earthdok, 2015-01-27 20:21:51]

found another instance while I was at it

[jln (very slow on Chromium), 2015-01-28 01:57:44]

lgtm

[Alexander Potapenko, 2015-01-28 11:14:01]

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

[Alexander Potapenko, 2015-01-28 11:14:02]

LGTM

[earthdok, 2015-01-28 15:32:44]

The CQ bit was checked by earthdok@chromium.org

[commit-bot: I haz the power, 2015-01-28 15:33:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/880023003/1

[commit-bot: I haz the power, 2015-01-28 15:34:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-28 15:36:04]

Patchset 1 (id:??) landed as
https://crrev.com/65f9d720f95b3c6f8465ad2fe7d49ac098b51a31
Cr-Commit-Position: refs/heads/master@{#313517}