lib/api, lib/model: Avoid contention on filesystem for DB status call (ref #7270) (#7271)

This splits the ignore getting to two methods, one that loads from disk
(the old one) and one that just returns whatever is already loaded (the
new one). The folder summary service which is just interested in stats
now uses the latter method. This means that it, and API calls that call
it, does not get blocked by folder I/O.

lib/api/api.go

@@ -1218,7 +1218,7 @@ func (s *service) getDBIgnores(w http.ResponseWriter, r *http.Request) {
 
 	folder := qs.Get("folder")
 
-	lines, patterns, err := s.model.GetIgnores(folder)
+	lines, patterns, err := s.model.LoadIgnores(folder)
 	if err != nil && !ignore.IsParseError(err) {
 		http.Error(w, err.Error(), 500)
 		return