BUG/MINOR: quic: Unsent frame because of qc_build_frms()

BUG/MINOR: quic: Unsent frame because of qc_build_frms()

There are non already identified rare cases where qc_build_frms() does not manage
to size frames to be encoded in a packet leading qc_build_frm() to fail to add
such frame to the packet to be built. In such cases we must move back such
frames to their origin frame list passed as parameter to qc_build_frms(): <frms>.
because they were added to the packet frame list (but not built). If this
this packet is not retransmitted, the frame is lost for ever! Furthermore we must
not modify the buffer.