With the current approach of checking log entries we are not able to
check log entries in case of a failure. But is is important to assert
log messages in case of a failure. Having reasonable log messages
simplified troubleshooting.
Hence we add JenkinsLoggingRule.expect(substring) and check after the
base of that rule has been called.
This interfears with other rules also working with an expect approach,
like e.g. ExpectedException. Which violation is presented depends on
the order or the rules around the test case.
