REORG: server: attach servers in parse_server

Move server linked into proxy backend list outside of _srv_parse_init to
parse_server.

This is groundwork for dynamic servers support. There will be two
differences in case of a dynamic server :
- the server will be attached to the proxy list only at the very end of the
  operations when everything is ok
- the server will be directly attached to the end of the server proxy
  list
1 file changed