Title: #4807: [Backport][ipa-4-8] ipatests: fix the disable_dnssec_validation method
This PR was opened automatically because PR #4800 was pushed to master and backport to
ipa-4-8 is required.
To pull the PR as Git branch:
git remote add ghfreeipa https://github.com/freeipa/freeipa
git fetch ghfreeipa pull/4807/head:pr4807
git checkout pr4807