dirmngr: Support https for KS_FETCH.
* dirmngr/ks-engine-hkp.c (cert_log_cb): Move to ... * dirmngr/misc.c (cert_log_cb): here. * dirmngr/ks-engine-http.c (ks_http_fetch): Support 307-redirection and https.
Note that this requires that the root certificates are registered using
the --hkp-cacert option. Eventually we may introduce a separate
option to allow using different CAs for KS_FETCH and keyserver based
requests.