MINOR: quic: Rename functions which do not build only Handshake packets

Rename qc_build_hdshk_pkt() to qc_build_pkt() and qc_do_build_hdshk_pkt()
to qc_do_build_pkt().
Update their comments consequently.
Make qc_do_build_hdshk_pkt() BUG_ON() when it does not manage to build
a packet. This is a bug!
1 file changed