Allow SSH agent errors to surface.

This will allow users to know when their sessions dies because of
a non-functioning agent / stale environment variables.

BUG=None
TEST=Script emits an error message to stderr when ssh-add fails.

Change-Id: Ia1c7a642eb75a256e69730c6095ace09284558a2
Reviewed-on: https://gerrit.chromium.org/gerrit/31621
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Ready: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
1 file changed