BUG/MINOR: resolvers: Set port before IP address when processing SRV records

BUG/MINOR: resolvers: Set port before IP address when processing SRV records

For a server subject to SRV resolution, when the server's address is set,
its dynamic cookie, if any, and its server key are computed. Both are based
on the ip/port pair. However, this happens before the server's port is
set. Thus the port is equal to 0 at this stage. It is a problem if several
servers share the same IP but with different ports because they will share
the same dynamic cookie and the same server key, disturbing this way the
connection persistency and the session stickiness.

This patch must be backported as far as 2.2.