certmonger: remove temporary workaround
    
    During recent refactoring, a workaround was added to make it
    possible for OpenSSL backend of python-cryptography to read PEM
    certificates returned by dogtag-ipa-renew-agent-submit. This was
    fixed in latest certmonger version.
    
    Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>