Allow filters to be used with binlogrouter

Filters can now be used with the binlogrouter to modify the contents of
the binlog stream now that the correct function call is used.

server/modules/routing/binlogrouter/blr_master.c

@@ -1974,7 +1974,7 @@ bool blr_send_packet(ROUTER_SLAVE *slave, uint8_t *buf, uint32_t len, bool first
         }
 
         slave->stats.n_bytes += GWBUF_LENGTH(buffer);
-        slave->dcb->func.write(slave->dcb, buffer);
+        MXS_SESSION_ROUTE_REPLY(slave->dcb->session, buffer);
     }
     else
     {