Revert "win pipe: race condition on queueing uv_pipe_zero_readfile_thread_proc"

This reverts commit dd0702a.

See discussion at JuliaLang/libuv@de067bc#commitcomment-14457130

Author: tkelman

Diff for: src/win/pipe.c

@@ -1114,6 +1114,7 @@ static DWORD WINAPI uv_pipe_zero_readfile_thread_proc(void* parameter) {
   assert(handle->type == UV_NAMED_PIPE);
 
   if (handle->flags & UV_HANDLE_PIPE_READ_CANCELABLE) {
+    uv_mutex_lock(m); /* mutex controls *setting* of readfile_thread */
     if (DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
                         GetCurrentProcess(), &hThread,
                         0, TRUE, DUPLICATE_SAME_ACCESS)) {
@@ -1247,13 +1248,9 @@ static void uv_pipe_queue_read(uv_loop_t* loop, uv_pipe_t* handle) {
   req = &handle->read_req;
 
   if (handle->flags & UV_HANDLE_NON_OVERLAPPED_PIPE) {
-    if (handle->flags & UV_HANDLE_PIPE_READ_CANCELABLE)
-        uv_mutex_lock(&handle->pipe.conn.readfile_mutex); /* mutex controls *setting* of readfile_thread */
     if (!QueueUserWorkItem(&uv_pipe_zero_readfile_thread_proc,
                            req,
                            WT_EXECUTELONGFUNCTION)) {
-      if (handle->flags & UV_HANDLE_PIPE_READ_CANCELABLE)
-          uv_mutex_unlock(&handle->pipe.conn.readfile_mutex);
       /* Make this req pending reporting an error. */
       SET_REQ_ERROR(req, GetLastError());
       goto error;