Fix intermittently failing variables-notembedded test case.

After sending packet that is too large, clienrt can get either an error packet with 
ER_NET_PACKET_TOO_LARGE, or a socket error. Both cases are valid, since the
server does not ensure reply was fully read by client, before shutting down  and closing 
the socket.

mysql-test/r/variables-notembedded.result

@@ -125,7 +125,7 @@ max_allowed_packet	2048
 SHOW SESSION VARIABLES LIKE 'net_buffer_length';
 Variable_name	Value
 net_buffer_length	4096
-ERROR 08S01: Got a packet bigger than 'max_allowed_packet' bytes
+Got one of the listed errors
 SELECT LENGTH(a) FROM t1;
 LENGTH(a)
 SET GLOBAL max_allowed_packet=default;