MFH: r545759

net/chrony: security update to 3.5.1

This upstream update essentially contains one Git commit:
https://git.tuxfamily.org/chrony/chrony.git/commit/?h=3.5-stable&id=f00fed20092b6a42283f29c6ee1f58244d74b545

It is to fix a symlink vulnerability when writing the pidfile.

Changelog: https://listengine.tuxfamily.org/chrony.tuxfamily.org/chrony-announce/2020/08/msg00000.html

Security: CVE-2020-14367
Security: 719f06af-e45e-11ea-95a1-c3b8167b8026

Approved by: ports-secteam (blanket, upstream update contains only security fix)