socket: use poll() instead of select() except on Windows (#2865)

Fixes #2278, which was originally addressed in #2279, but was not
properly merged. Additionally it did not address the problem
of poll not existing on Windows. This patch falls back on the
more limited select method if host system is Windows.

Signed-off-by: Tyler Westland <tylerofthewest@gmail.com>

docker/utils/socket.py

@@ -3,6 +3,7 @@ import os
 import select
 import socket as pysocket
 import struct
+import sys
 
 try:
     from ..transport import NpipeSocket
@@ -31,7 +32,13 @@ def read(socket, n=4096):
     recoverable_errors = (errno.EINTR, errno.EDEADLK, errno.EWOULDBLOCK)
 
     if not isinstance(socket, NpipeSocket):
-        select.select([socket], [], [])
+        if sys.platform == 'win32':
+            # Limited to 1024
+            select.select([socket], [], [])
+        else:
+            poll = select.poll()
+            poll.register(socket)
+            poll.poll()
 
     try:
         if hasattr(socket, 'recv'):