Extract from ssl/del_ssl_crt-list.vtc the common part to produce
ssl/del_ssl_crt-list.vtci which may be reused by QUIC and TCP
from respectively quic/del_ssl_crt-list.vtc and ssl/del_ssl_crt-list.vtc
thanks to "include" VTC command and VTC_SOCK_TYPE special vtest environment
variable.
