12071 clarify implementation of single_instance in SMF services
Reviewed by: Robert Mustacchi <rm@fingolfin.org>

*** 19,29 ****
   * CDDL HEADER END
   */
  
  /*
   * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
!  * Copyright 2015 Joyent, Inc.
   * Copyright 2012 Milan Jurik. All rights reserved.
   * Copyright 2017 RackTop Systems.
   * Copyright 2018 OmniOS Community Edition (OmniOSce) Association.
   */
  
--- 19,29 ----
   * CDDL HEADER END
   */
  
  /*
   * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
!  * Copyright 2019 Joyent, Inc.
   * Copyright 2012 Milan Jurik. All rights reserved.
   * Copyright 2017 RackTop Systems.
   * Copyright 2018 OmniOS Community Edition (OmniOSce) Association.
   */
  
*** 9741,9750 ****
--- 9741,9754 ----
          while ((ret = scf_iter_next_property(exp_prop_iter, exp_prop)) == 1) {
                  if (scf_property_get_name(exp_prop, exp_str, exp_str_sz) < 0)
                          scfdie();
  
                  if (strcmp(exp_str, SCF_PROPERTY_SINGLE_INSTANCE) == 0) {
+                         /*
+                          * Unimplemented and obsolete, but we still process it
+                          * for compatibility purposes.
+                          */
                          if (prop_check_type(exp_prop, SCF_TYPE_BOOLEAN) == 0 &&
                              prop_get_val(exp_prop, exp_val) == 0) {
                                  uint8_t b;
  
                                  if (scf_value_get_boolean(exp_val, &b) !=