Fix bug with invalid "location" field instead of "state" field in some

Fix bug with invalid "location" field instead of "state" field in some
cases of unittests.
At the current time it works only because numerical value for
Manifest::EXTERNAL_PREF, which is right location value for test
extensions, is equal to Extension::EXTERNAL_EXTENSION_UNINSTALLED
which needs to validate.

BUG=
R=aa@chromium.org,yoz@chromium.org

Committed: https://crrev.com/65392a071925908e8e406f6419365bbde6275699
Cr-Commit-Position: refs/heads/master@{#293402}

[Yoyo Zhou, 2014-09-04 20:56:28]

LGTM, nice catch.

[Yoyo Zhou, 2014-09-04 20:56:37]

The CQ bit was checked by yoz@chromium.org

[commit-bot: I haz the power, 2014-09-04 20:58:20]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/reat@yandex-team.ru/534993003/1

[commit-bot: I haz the power, 2014-09-05 02:14:07]

Committed patchset #1 (id:1) as 76100ead0f7d36061fe9c31c5053390d835aed0d

[commit-bot: I haz the power, 2014-09-10 03:35:38]

Patchset 1 (id:??) landed as
https://crrev.com/65392a071925908e8e406f6419365bbde6275699
Cr-Commit-Position: refs/heads/master@{#293402}