Make intermittently failing tests more stable to avoid failed builds

[joelpurra]

When running build tests on commit/push, some of the tests fail due to unexpected (non-)timeouts thus "failing" the entire build suite. Due to the nature of the tests, testing against "real world" domain names etcetera, it would be good if these intermittently failing tests can be identified and made more stable.

Instead of annoying developers with failing tests, perhaps timeouts can be increased -- and perhaps even automatic retries for certain tests?

[joelpurra]

The DNS lookup tests cases themselves seem to be fairly stable, and pass most of the time. Instead there is a problem with a SIGSEGV happening every once in a while. Seems to happen more often on the build server than on my local dev machine.

See #24.