looking for non-standard-named depot_tools directory
in git cl hooks python script.  Otherwise, python
ignores the path.

Patch contributed by James Jones @ nvidia.

BUG=chromium-os:7007

Review URL: http://codereview.chromium.org/3467013

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@60499 0039d316-1c4b-4281-b951-d872f2087c98