https-dns-proxy: upstream bugfix for ca_info

* upstream bugfix: Add a forgotten 'NULL' initialize for ca_info
  if not manually set
* make init script PKG_VERSION variable readonly so that a
  shellcheck excettion can be removed
* add procd interface trigger to 'wan6' if IPv6 wan interface name
  cannot be obtained on start

Signed-off-by: Stan Grishin <stangri@melmac.ca>