MINOR: http: Switch requests/responses in TUNNEL mode only by checking txn flags

Today, the only way to have a request or a response in HTTP_MSG_TUNNEL state is
to have the flag TX_CON_WANT_TUN set on the transaction. So this is a symmetric
state. Both the request and the response are switch in same time in this
state. This can be done only by checking transaction flags instead of relying on
the other side state. This is the purpose of this patch.

This way, if for any reason we need to switch only one side in TUNNEL mode, it
will be possible. And to prepare asymmetric cases, we check channel flags in
DONE _AND_ TUNNEL states.

WARNING: This patch will be used to fix a bug. The fix will be commited in a
very next commit. So if the fix is backported, this one must be backported too.
1 file changed