[patch] Use err instead of errx for checking strdup failed

[Nan Xiao]

Hi tech@,

Following is a trivial modification of tcpbench.c, and I think use err
is more better than errx. Apologize if I am wrong, thanks!

Index: tcpbench.c
===================================================================
RCS file: /cvs/src/usr.bin/tcpbench/tcpbench.c,v
retrieving revision 1.52
diff -u -p -r1.52 tcpbench.c
--- tcpbench.c  19 Sep 2016 18:58:39 -0000      1.52
+++ tcpbench.c  10 May 2018 09:41:42 -0000
@@ -1041,7 +1041,7 @@ main(int argc, char **argv)
                        exit(0);
                case 'k':
                        if ((tmp = strdup(optarg)) == NULL)
-                               errx(1, "strdup");
+                               err(1, "strdup");
                        ptb->kvars = check_prepare_kvars(tmp);
                        free(tmp);
                        break;


-- 
Best Regards
Nan Xiao