Set explicit confdir option for global contexts
    
    Some API contexts are used to modify global state (e.g. files in /etc
    and /var). These contexts do not support confdir overrides. Initialize
    the API with an explicit confdir argument to paths.ETC_IPA.
    
    The special contexts are:
    
    * backup
    * cli_installer
    * installer
    * ipctl
    * renew
    * restore
    * server
    * updates
    
    The patch also corrects the context of the ipa-httpd-kdcproxy script to
    'server'.
    
    https://fedorahosted.org/freeipa/ticket/6389
    
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>