Autotest: Fix Reimager Timeout.

Now that we pre-assign hosts to be used in a try job we need to add
the reimager timeout code to wait_for_jobs_to_finish.

Also reduced timeout time to 2 hours instead of 4.

BUG=chromium:240759
TEST=current unit tests & local setup.

Change-Id: I7b236a2975de05c0144742fee4eead69a3e4f954
Reviewed-on: https://gerrit.chromium.org/gerrit/57019
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Simran Basi <sbasi@chromium.org>
4 files changed