validation_pool.py: shorten the timeout on submitting a patch

Given that we treat a timed out SUBMIT as thought the patch was
submitted, and are hitting this timeout quite often, there doesn't seem
to be much point in waiting so long. See for instance
http://goo.gl/1Taz3k

BUG=None
TEST=None

Change-Id: Iaaede53c62abd0962de4e85fafcfa6dad60b7da1
Reviewed-on: https://chromium-review.googlesource.com/191109
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Yu-Ju Hong <yjhong@chromium.org>
Commit-Queue: Aviv Keshet <akeshet@chromium.org>
1 file changed