XEP-0198: Change state immediately when gen_tcp:send/2 returns failure

When Stream Management is enabled and a `gen_tcp:send/2` call fails, go into the `wait_for_resume` state immediately.  This makes sure that `gen_tcp:send/2` won't be called again, which might avoid an Erlang issue where `gen_tcp:send/2` apparently hangs despite `send_timeout` (and `send_timeout_close`) being set.