Run the callback last in infc_request_manager_fail_request
Run the callback last in infc_request_manager_fail_request

Otherwise it can happen that the callback deletes the request manager itself,
and the following attempt to remove the request from the manager would fail.

gobby/libinfinity,tyll/libinfinity,tyll/libinfinity,gobby/libinfinity,gobby/libinfinity,tyll/libinfinity