MINOR: server: return the next srv instance on free_server

As a convenience, return the next server instance from servers list on
free_server.

This is particularily useful when using this function on the servers
list without having to save of the next pointer before calling it.

(cherry picked from commit f5c1e12e44e1caa0185e063daf00fb8841c2ed3d)
[ad: updated context: remove uneeded condition on srv]
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
3 files changed