fix(admission): use client network, fail-open on nil gRPC client, close http resources

- Use client address network instead of listener network in admission wrapper
- Return true (allow) when gRPC admission plugin client is nil to fail-open
- Add Close() to httpPlugin to close idle HTTP connections
- Close httpLoader in localAdmission.Close()
- Remove dead commented-out code in periodReload

admission/admission.go

@@ -145,7 +145,6 @@ func (p *localAdmission) periodReload(ctx context.Context) error {
 		case <-ticker.C:
 			if err := p.reload(ctx); err != nil {
 				p.logger.Warnf("reload: %v", err)
-				// return err
 			}
 		case <-ctx.Done():
 			return ctx.Err()
@@ -279,6 +278,9 @@ func (p *localAdmission) Close() error {
 	if p.options.redisLoader != nil {
 		p.options.redisLoader.Close()
 	}
+	if p.options.httpLoader != nil {
+		p.options.httpLoader.Close()
+	}
 	return nil
 }