tcpdump: Initialize tzcode early.

An explicit tzset() call is usually not needed as it happens implicitly
the first time we call localtime() or mktime(), but in some cases
(sandboxing, chroot) this may be too late.

PR:		273807
MFC after:	3 days
Reviewed by:	jrm
Differential Revision:	https://reviews.freebsd.org/D41880
Approved by:	re (kib)

(cherry picked from commit 7e0a7ef)
(cherry picked from commit 51d54ed)

contrib/tcpdump/tcpdump.c

@@ -1564,6 +1564,8 @@ main(int argc, char **argv)
 	if (abort_on_misalignment(ebuf, sizeof(ebuf)) < 0)
 		error("%s", ebuf);
 
+	tzset();
+
 	while (
 	    (op = getopt_long(argc, argv, SHORTOPTS, longopts, NULL)) != -1)
 		switch (op) {