Fix to bug #463, http://bugs.skysql.com/show_bug.cgi?id=463

mysql_common.c:gw_MySQL_get_next_packet didn't handle case where an insert command followed by alter table in the same read buffer. It shouldn't been possible without multi-statement being set.

server/modules/routing/readwritesplit/readwritesplit.c

@@ -1550,6 +1550,8 @@ static void clientReply (
                         char*    cmdstr = (char *)malloc(len+1);
                         /** data+termination character == len */
                         snprintf(cmdstr, len, "%s", &buf[5]);
+
+                        ss_dassert(len+4 == GWBUF_LENGTH(scur->scmd_cur_cmd->my_sescmd_buf));
                         
                         LOGIF(LE, (skygw_log_write_flush(
                                 LOGFILE_ERROR,