BUG/MEDIUM: server: fix dynamic servers initial settings

Contrary to static servers, dynamic servers does not initialize their
settings from a default server instance. As such, _srv_parse_init() was
responsible to set a set of minimal values to have a correct behavior.

However, some settings were not properly initialized. This caused
dynamic servers to not behave as static ones without explicit
parameters.

Currently, the main issue detected is connection reuse which was
completely impossible. This is due to incorrect pool_purge_delay and
max_reuse settings incompatible with srv_add_to_idle_list().

To fix the connection reuse, but also more generally to ensure dynamic
servers are aligned with other server instances, define a new function
srv_settings_init(). This is used to set initial values for both default
servers and dynamic servers. For static servers, srv_settings_cpy() is
kept instead, using their default server as reference.

This patch could have unexpected effects on dynamic servers behavior as
it restored proper initial settings. Previously, they were set to 0 via
calloc() invocation from new_server().

This should be backported up to 2.6, after a brief period of
observation.

(cherry picked from commit 8a31783b647f3bef171a7faf074da2b1563f8a80)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 2ac63e336f04c2985867f80e9e40bcfd1e53b946)
 [ad: remove pp_tlvs server member]
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
3 files changed