Add router cache back for performance comparision (#2036)

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

Co-authored-by: Vishal <vishal-biyani@users.noreply.github.com>

pkg/router/functionServiceMap.go

@@ -77,3 +77,8 @@ func (fmap *functionServiceMap) assign(f *metav1.ObjectMeta, serviceURL *url.URL
 		// ignore error
 	}
 }
+
+func (fmap *functionServiceMap) remove(f *metav1.ObjectMeta) error {
+	mk := keyFromMetadata(f)
+	return fmap.cache.Delete(*mk)
+}