Add IPA helper for server install
    
    The IPa helper chcks a krb keytab is available for the local HTTPD
    service at the standard ipa location, and if not available, tries
    to register the sevice and retrieve one from the IPA server.
    
    At the end of the process forces the activation of the krb plugin
    as well as the fallback to pam for authentication.
    
    Signed-off-by: Simo Sorce <simo@redhat.com>