10921 mdb_nicenum() needs smatch fix

@@ -21,10 +21,11 @@
 
 /*
  * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright 2016 Nexenta Systems, Inc.  All rights reserved.
+ * Copyright 2019 Joyent, Inc.
  */
 
 #include <mdb/mdb_modapi.h>
 #include <mdb/mdb_module.h>
 #include <mdb/mdb_string.h>

@@ -90,15 +91,15 @@
                 (void) mdb_snprintf(buf, MDB_NICENUM_BUFLEN, "%llu",
                     (u_longlong_t)n);
         } else if (n < 10 && (num & (num - 1)) != 0) {
                 (void) mdb_snprintfrac(buf, MDB_NICENUM_BUFLEN,
                     num, 1ULL << 10 * index, 2);
-                strcat(buf, u);
+                (void) strcat(buf, u);
         } else if (n < 100 && (num & (num - 1)) != 0) {
                 (void) mdb_snprintfrac(buf, MDB_NICENUM_BUFLEN,
                     num, 1ULL << 10 * index, 1);
-                strcat(buf, u);
+                (void) strcat(buf, u);
         } else {
                 (void) mdb_snprintf(buf, MDB_NICENUM_BUFLEN, "%llu%s",
                     (u_longlong_t)n, u);
         }
 }