check_dns: added test for nonresponsive dns server (#982)

Signed-off-by: Sven Nierlein <sven@nierlein.de>
travis-ci: create MySQL database 'test'
check_dns: returns incorrect state when specifying server

This patch verifies if the response is returned by the dns server we
are trying to check
---
Closes #981
Closes #982
Closes #1164
adding to THANKS