BUG/MEDIUM: quic: do not drop packet on duplicate stream/decoding error

BUG/MEDIUM: quic: do not drop packet on duplicate stream/decoding error

Change the return value to success in qc_handle_bidi_strm_frm for two
specific cases :
* if STREAM frame is an already received offset
* if application decoding failed

This ensures that the packet is not dropped and properly acknowledged.
Previous to this fix, the return code was set to error which prevented
the ACK to be generated.

The impact of the bug might be noticeable in environment with packet
loss and retransmission. Due to haproxy not generating ACK for packets
containing STREAM frames with already received offset, the client will
probably retransmit them again, which will worsen the network
transmission.