auth api: flush all caches when flushing

So far we never flushed the DNSSEC caches, except when DELETEing a domain.
However clearly some operations can affect the DNSSEC settings, and then the
caches should go.

Also do this for the flush API, to be consistent, and for users writing to the
DNSSEC settings/data externally.

pdns/ws-auth.cc

@@ -2331,6 +2331,7 @@ static void patchZone(UeberBackend& B, const DNSName& zonename, DomainInfo& di,
 
   di.backend->commitTransaction();
 
+  DNSSECKeeper::clearCaches(zonename);
   purgeAuthCaches(zonename.toString() + "$");
 
   resp->body = "";
@@ -2459,6 +2460,7 @@ static void apiServerCacheFlush(HttpRequest* req, HttpResponse* resp) {
     }
   }
 
+  DNSSECKeeper::clearCaches(canon);
   // purge entire zone from cache, not just zone-level records.
   uint64_t count = purgeAuthCaches(canon.toString() + "$");
   resp->setJsonBody(Json::object {