sdig: allow cleartext DoH to work when dnsdist is using nghttp2 as lib

[omoerbeek]

When dnsdist uses nghttp2 as a http(s) lib, it does not accept HTTP/1. This has the consequence that when dnsdist is configured to use clear-text incoming DoH sdig cannot query it, as defaults to use ALPN, which does not work. Remedy is to set:

curl_easy_setopt(getCURLPtr(d_curl), CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE);

in minicurl.cc. It remains to be decided if that should be an option to sdig or if we should set that always (which would break HTTP/1 DoH connections, but those are fishy anyway).

[Habbie]

sdig is not the only user of minicurl - LUA records ifurlup and friends rely on it as well, and maybe rec zoneToCache too? we need to make sure we don't break any of those