ci: add timestamps in bare metal agents
Created by: jhchabran
Fixes #26891 (closed)
This is a crude fix, a better one would be to update the configuration (see this PR https://github.com/sourcegraph/infrastructure/pull/2867) but I'm not entirely sure this won't mess up with Vagrant logs in some way. I'll check with @davejrt.
In the meantime, this PR fixes the problem.