More shared functions and test log readability

[hhorak]

This combines two changes that both improve test script, so I did not bother to split it to two commits. One is using more functions from the test-lib shared library, and second is removing expected warnings from the test log, to make the log more readable and easier to spot the issues.

This PR builds on top of #544 and #543 (to avoid merge conflicts), and those PRs must be merged before.