unix: remove overzealous assert

Several node.js users are hitting this assert under what appear to be
mostly benign conditions. In other words, it's unclear whether it's
catching real bugs or just has wrong expectations.

An aborting process is rather disruptive so I'm removing the assert
from the stable branch and relanding it in the master branch.

src/unix/stream.c

@@ -1318,16 +1318,6 @@ int uv_read2_start(uv_stream_t* stream, uv_alloc_cb alloc_cb,
 
 
 int uv_read_stop(uv_stream_t* stream) {
-  /* Sanity check. We're going to stop the handle unless it's primed for
-   * writing but that means there should be some kind of write action in
-   * progress.
-   */
-  assert(!uv__io_active(&stream->io_watcher, UV__POLLOUT) ||
-         !ngx_queue_empty(&stream->write_completed_queue) ||
-         !ngx_queue_empty(&stream->write_queue) ||
-         stream->shutdown_req != NULL ||
-         stream->connect_req != NULL);
-
   stream->flags &= ~UV_STREAM_READING;
   uv__io_stop(stream->loop, &stream->io_watcher, UV__POLLIN);
   if (!uv__io_active(&stream->io_watcher, UV__POLLOUT))