Document envtest defaults

Author: Maria Ntalla

pkg/envtest/server.go

@@ -39,9 +39,9 @@ It's possible to override some defaults, by setting the following environment va
 	TEST_ASSET_KUBE_APISERVER (string): path to the api-server binary to use
 	TEST_ASSET_ETCD (string): path to the etcd binary to use
 	TEST_ASSET_KUBECTL (string): path to the kubectl binary to use
-	KUBEBUILDER_ASSETS (string): directory containing the binaries to use (api-server, etcd and kubectl)
-	KUBEBUILDER_CONTROLPLANE_START_TIMEOUT (string supported by time.ParseDuration): timeout for test control plane to start
-	KUBEBUILDER_CONTROLPLANE_STOP_TIMEOUT (string supported by time.ParseDuration): timeout for test control plane to start
+	KUBEBUILDER_ASSETS (string): directory containing the binaries to use (api-server, etcd and kubectl). Defaults to /usr/local/kubebuilder/bin.
+	KUBEBUILDER_CONTROLPLANE_START_TIMEOUT (string supported by time.ParseDuration): timeout for test control plane to start. Defaults to 20s.
+	KUBEBUILDER_CONTROLPLANE_STOP_TIMEOUT (string supported by time.ParseDuration): timeout for test control plane to start. Defaults to 20s.
 	KUBEBUILDER_ATTACH_CONTROL_PLANE_OUTPUT (boolean): if set to true, the control plane's stdout and stderr are attached to os.Stdout and os.Stderr
 
 */