libcmd: Don't increment array then discard result

We don't need to increment argv here, as we're about to return
to the caller.

Change-Id: I442fe741e4bda91e12375a6fe72657dc215c4e78
Reviewed-on: http://gerrit.openafs.org/5078
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>

src/cmd/cmd.c

@@ -1159,7 +1159,7 @@ CopyBackArgs(struct cmd_token *alist, char **argv,
 	argv++;
 	count++;
     }
-    *(argv++) = 0;		/* use last slot for terminating null */
+    *argv = NULL;		/* use last slot for terminating null */
     /* don't count terminating null */
     *an = count;
     return 0;