MEDIUM: mux-h2: Close streams when processing data for an aborted tunnel

MEDIUM: mux-h2: Close streams when processing data for an aborted tunnel

In the previous patch ("MEDIUM: mux-h2: Block client data on server side
waiting tunnel establishment"), we added a way to block client data for not
fully established tunnel on the server side. This one closes the stream with
an ERR_CANCEL erorr if there are some pending tunneled data while the tunnel
was aborted. This may happen on the client side if a non-empty DATA frame or
an empty DATA frame without the ES flag is received. This may also happen on
the server side if there is a DATA htx block. However in this last case, we
first wait the response is fully forwarded.

This patch contributes to fix the tunnel mode between the H1 and the H2
muxes.