db update requires own download logic for prefetch, previous logic caused check for updates to use old database and all databases were being updated before all repos were checked for cached pkgs

internal/repomaint/repomaint_test.go

@@ -19,7 +19,7 @@ type mockCache struct {
 	fetchDBCalled bool
 }
 
-func (m *mockCache) FetchDB() error {
+func (m *mockCache) FetchDB(repo string) error {
 	m.fetchDBCalled = true
 	return nil
 }