[Backport] Ignore timeout error when receiving message

Bug has been fixed in oslo.privsep 1.14.0, this patch intends
to backport this patch in stable/newton.

When the clientchannel's receiver thread had crashed with
timeout error. the upside main procedure will contine with-
out any notifications, it may get stucked when no thread can
handle the messages later on.

This change just fix this situation by ignore the timeout
exception.

Change-Id: Ie6058c9b9ffeac7c9af8b3ca9f40ea2b3c940ec2
Closes-Bug: #1645172
(cherry picked from commit 3b53619017)

oslo_privsep/comm.py

@@ -74,10 +74,13 @@ class Deserializer(six.Iterator):
             try:
                 return next(self.unpacker)
             except StopIteration:
-                buf = self.readsock.recv(4096)
-                if not buf:
-                    raise
-                self.unpacker.feed(buf)
+                try:
+                    buf = self.readsock.recv(4096)
+                    if not buf:
+                        raise
+                    self.unpacker.feed(buf)
+                except socket.timeout:
+                    pass
 
 
 class Future(object):