darwin: remove EPROTOTYPE error workaround (#3405)

It's been reported in the past that OS X 10.10, because of a race
condition in the XNU kernel, sometimes returns a transient EPROTOTYPE
error when trying to write to a socket. Libuv handles that by retrying
the operation until it succeeds or fails with a different error.

Recently it's been reported that current versions of the operating
system formerly known as OS X fail permanently with EPROTOTYPE under
certain conditions, resulting in an infinite loop.

Because Apple isn't exactly forthcoming with bug fixes or even details,
I'm opting to simply remove the workaround and have the error bubble up.

Refs: #482

src/unix/stream.c

@@ -58,20 +58,6 @@ struct uv__stream_select_s {
   fd_set* swrite;
   size_t swrite_sz;
 };
-
-/* Due to a possible kernel bug at least in OS X 10.10 "Yosemite",
- * EPROTOTYPE can be returned while trying to write to a socket that is
- * shutting down. If we retry the write, we should get the expected EPIPE
- * instead.
- */
-# define RETRY_ON_WRITE_ERROR(errno) (errno == EINTR || errno == EPROTOTYPE)
-# define IS_TRANSIENT_WRITE_ERROR(errno, send_handle) \
-    (errno == EAGAIN || errno == EWOULDBLOCK || errno == ENOBUFS || \
-     (errno == EMSGSIZE && send_handle != NULL))
-#else
-# define RETRY_ON_WRITE_ERROR(errno) (errno == EINTR)
-# define IS_TRANSIENT_WRITE_ERROR(errno, send_handle) \
-    (errno == EAGAIN || errno == EWOULDBLOCK || errno == ENOBUFS)
 #endif /* defined(__APPLE__) */
 
 static void uv__stream_connect(uv_stream_t*);
@@ -866,17 +852,17 @@ static int uv__try_write(uv_stream_t* stream,
 
     do
       n = sendmsg(uv__stream_fd(stream), &msg, 0);
-    while (n == -1 && RETRY_ON_WRITE_ERROR(errno));
+    while (n == -1 && errno == EINTR);
   } else {
     do
       n = uv__writev(uv__stream_fd(stream), iov, iovcnt);
-    while (n == -1 && RETRY_ON_WRITE_ERROR(errno));
+    while (n == -1 && errno == EINTR);
   }
 
   if (n >= 0)
     return n;
 
-  if (IS_TRANSIENT_WRITE_ERROR(errno, send_handle))
+  if (errno == EAGAIN || errno == EWOULDBLOCK || errno == ENOBUFS)
     return UV_EAGAIN;
 
   return UV__ERR(errno);