Reduce logging in integration tests

[aarongable]

trafficstars

Ideas:

• shorten log line prefix (esp the rsyslog-added prefix)
• lower log level overall, esp in the CA
• when tests fail, send sigkill instead of sigterm for less-graceful and less-verbose shutdown

[jsha]

We could condition the different logging code on the integration build tag.

One possible stumbling block: we do have code that collects log output and parses it (e.g. test-caa-log-checker). We would have to make sure it accepts both prod and dev style logs.

Another item for the list:

• In the integration test, don't print stack traces on errors. Or rather catch exceptions and render them as a plain error (plus maybe the single line that originated it).
• Also when the Go integration tests fail, don't print additional output from the Python orchestrator.