Assert during SUB socket termination fixed.

Fair queueing algorithm was checking whether the current pipe
is not closed in the middle of reading a multipart message.
However, this is OK when the socket is closing down.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

src/fq.cpp

@@ -55,10 +55,9 @@ void zmq::fq_t::attach (reader_t *pipe_)
 
 void zmq::fq_t::terminated (reader_t *pipe_)
 {
-    //  TODO: This is a problem with session-initiated termination. It breaks
-    //  message atomicity. However, for socket initiated termination it's
-    //  just fine.
-    zmq_assert (!more || pipes [current] != pipe_);
+    //  Make sure that we are not closing current pipe while
+    //  message is half-read.
+    zmq_assert (terminating || (!more || pipes [current] != pipe_));
 
     //  Remove the pipe from the list; adjust number of active pipes
     //  accordingly.