* dirmngr/ks-engine.h (KS_HTTP_FETCH_NOCACHE): New flag.
(KS_HTTP_FETCH_TRUST_CFG): Ditto.
(KS_HTTP_FETCH_NO_CRL): Ditto.
(KS_HTTP_FETCH_ALLOW_DOWNGRADE): Ditto.
* dirmngr/ks-engine-http.c (ks_http_fetch): Replace args send_no_cache
and extra_http_trust_flags by a new flags arg.  Allow redirectiong
from https to http it KS_HTTP_FETCH_ALLOW_DOWNGRADE is set.
* dirmngr/loadswdb.c (fetch_file): Call with KS_HTTP_FETCH_NOCACHE.
* dirmngr/ks-action.c (ks_action_get): Ditto.
(ks_action_fetch): Ditto.
* dirmngr/crlfetch.c (crl_fetch): Call with the appropriate flags.