net/chrony: fix "socket" test and re-enable

In the socket test, make the sockets blocking to avoid spurious
test failures. Cherry-picked from upstream Git, with
the actual diff body regenerated in the ports framework.

Obtained from: Miroslav Lichvar (upstream maintainer)
https://gitlab.com/chrony/chrony/-/commit/120bf44989391164c924e97d3142dc1352ab7970
https://listengine.tuxfamily.org/chrony.tuxfamily.org/chrony-users/2025/08/msg00024.html