BUG/MINOR: mux-h1: Don't stop anymore input processing when the max is reached

BUG/MINOR: mux-h1: Don't stop anymore input processing when the max is reached

The loop is now stopped only when nothing else is consumed from the input buffer
or if a parsing error is encountered. This will let a chance to detect cases
when we fail to add the EOM.

For instance, when the max is reached after the headers parsing and all the
message is received. In this case, we may have the flag H1S_F_REOS set without
the flag H1S_F_APPEND_EOM and no pending input data, leading to an error because
we think it is an abort.

This patch must be backported to 2.0. This bug does not affect 1.9.