BUG/MINOR: mux-h1: Fix tunnel mode detection on the response path

There are two issues with the way tunnel mode is detected on the response
path. First, when a response with an unknown content length is handled, the
request is also switched in tunnel mode. It is obviously wrong. Because it was
done on the server side only (so not during the request parsing), it is no
noticeable effects.

The second issue is about the way protocol upgrades are handled. The request is
switched in tunnel mode from the time the 101 response is processed. So an
unfinished request may be switched in tunnel mode too early. It is not a common
use, but a protocol upgrade on a POST is allowed. Thus, parsing of the payload
may be hijacked. It is especially bad for chunked payloads.

Now, conditions to switch the request in tunnel mode reflect what should be
done. Especially for the second issue. We wait the end of the request to switch
it in tunnel mode.

This patch must be backported to 2.0 and 1.9. Note that these versions are only
affected by the second issue but the patch cannot be easily splitted.
1 file changed