CAless installation: set the perms on KDC cert file
    
    In CA less installation, the KDC certificate file does not have
    the expected 644 permissions. As a consequence, WebUI login
    fails.
    
    The fix makes sure that the KDC cert file is saved with 644 perms.
    
    Fixes: https://pagure.io/freeipa/issue/8440
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>