unix: ignore ECONNABORTED errors from accept()

ECONNABORTED means that the connection was torn down by the peer before the
TCP handshake completed. Ignore it, there's nothing we can do and it simplifies
error handling for libuv users.

src/unix/stream.c

@@ -185,6 +185,9 @@ void uv__server_io(EV_P_ ev_io* watcher, int revents) {
       } else if (errno == EMFILE) {
         /* TODO special trick. unlock reserved socket, accept, close. */
         return;
+      } else if (errno == ECONNABORTED) {
+        /* ignore */
+        continue;
       } else {
         uv__set_sys_error(stream->loop, errno);
         stream->connection_cb((uv_stream_t*)stream, -1);