e2e: node: expose the running flag

Each e2e test knows it wants to restart a running kubelet or a
non-running kubelet. The vast majority of times, we want to
restart a running kubelet (e.g. to change config or to check
some properties hold across kubelet crashes/restarts), but sometimes
we stop the kubelet, do some actions and only then restart.

To accomodate both use cases, we just expose the `running` boolean
flag to the e2e tests.

Having the `restartKubelet` explicitly restarting a running kubelet
helps us to trobuleshoot e2e failures on which the kubelet
was supposed to be running, while it was not; attempting a restart
in such cases only murkied the waters further, making the
troubleshooting and the eventual fix harder.

In the happy path, no expected change in behaviour.

Signed-off-by: Francesco Romani <fromani@redhat.com>

test/e2e_node/device_plugin_test.go

@@ -220,7 +220,7 @@ func testDevicePlugin(f *framework.Framework, pluginSockDir string) {
 
 			restartTime := time.Now()
 			ginkgo.By("Restarting Kubelet")
-			restartKubelet()
+			restartKubelet(true)
 
 			// We need to wait for node to be ready before re-registering stub device plugin.
 			// Otherwise, Kubelet DeviceManager may remove the re-registered sockets after it starts.