Title: #1235: [Backport][ipa-4-6] prci: add external_ca test
This PR was opened automatically because PR #1027 was pushed to master and backport to
ipa-4-6 is required.
To pull the PR as Git branch:
git remote add ghfreeipa https://github.com/freeipa/freeipa
git fetch ghfreeipa pull/1235/head:pr1235
git checkout pr1235