Improve error handling in ipa-httpd-kdcproxy
    
    The pre start script 'ipa-httpd-kdcproxy' for httpd.service now handles
    connection and authentication errors more gracefully. If the script is
    not able to conenct to LDAP, it only prints a warning and exits with
    status code 0. All other errors are still reported as fatal error and
    result in a non-zero exit code.
    
    This fixes a problem with offline RPM updates. A restart of Apache no
    longer fails when LDAP is not running.
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>