add bidi attribute to change_type

when a non-bidi protocol used with a bidi protocol, if change_type doesn't change the bidi attribute of #state_rcv,
it may cause problems.

For the following config:
<session name="activity_browse" probability="100" type="ts_http">
        <change_type new_type="ts_websocket" host="127.0.0.1" port="8080" server_type="tcp" restore="true" store="true" />
        <request subst="true">
             <websocket type="connect" path="/chat"></websocket>
        </request>
        <thinktime value="15" random="true"/>
...
</session>

right after the 'connect' request finished, if the server send some data to the client, it will cause the connection to be closed.