QUIC: better sockaddr initialization. The qsock->sockaddr field is a ngx_sockaddr_t union, and therefore can hold any sockaddr (and union members, such qsock->sockaddr.sockaddr, can be used to access appropriate variant of the sockaddr). It is better to set it via qsock->sockaddr itself though, and not qsock->sockaddr.sockaddr, so static analyzers won't complain about out-of-bounds access. Prodded by Coverity (CID 1530403).