Title: #1111: ipalib.x509 autumn cleanup
This is a cleanup of the x509 module which removes an ugly hack that prevents a circular
dependency and the `strip_header()` function which is properly replaced by the
`load_unknown_x509_certificate()` function where needed.
To pull the PR as Git branch:
git remote add ghfreeipa https://github.com/freeipa/freeipa
git fetch ghfreeipa pull/1111/head:pr1111
git checkout pr1111