- add dispatcher modparam `ds_ping_socket` - add gateway param `ping_socket`

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#### Description

could be useful for HA use cases where multiple kamailio nodes share a common Virtual IP (e.g.: managed by the VRRP).

we need to route requests using Virtual IP socket configured with `ds_default_sockname`/`socket` and to perform destinations probing using self-IP socket configured with `ds_ping_socket`/`ping_socket`. You can view, comment on, or merge this pull request online at:

https://github.com/kamailio/kamailio/pull/4186

-- Commit Summary --

* dispatcher: added ping socket configuration

-- File Changes --

M src/modules/dispatcher/dispatch.c (32) M src/modules/dispatcher/dispatch.h (2) M src/modules/dispatcher/dispatcher.c (25) M src/modules/dispatcher/doc/dispatcher_admin.xml (20)

-- Patch Links --

https://github.com/kamailio/kamailio/pull/4186.patch https://github.com/kamailio/kamailio/pull/4186.diff