BUG/MINOR: server: Use the configured address family for the initial resolution

BUG/MINOR: server: Use the configured address family for the initial resolution

A regression was introduced by the commit c886fb58eb ("MINOR: server/ip:
centralize server ip updates"). The configured address family is lost when the
server address is initialized during the startup, for the resolution based on
the libc or based on the server state-file. Thus, "ipv4@" and "ipv6@" prefixed
are ignored.

To fix the bug, we take care to use the configured address family before calling
str2ip2() in srv_apply_lastaddr() and srv_apply_via_libc() functions.

This patch should fix the issue #2393. It must be backported to 2.9.