BUG/MAJOR: servers state: server port is erased when dns resolution is enabled on...

BUG/MAJOR: servers state: server port is erased when dns resolution is enabled on a server

Servers state function save and apply server IP when DNS resolution is
enabled on a server.
Purpose is to prevent switching traffic from one server to an other one
when multiple IPs are returned by the DNS server for the A or AAAA
record.

That said, a bug in current code lead to erase the service port while
copying the IP found in the file into the server structure in HAProxy's
memory.
This patch fix this bug.

The bug was reported on the ML by Robert Samuel Newson and fix proposed
by Nenad Merdanovic.
Thank you both!!!

backport: can be backported to 1.6