Add node expiry test

This commits adds a test to verify that nodes get updated if a node in
their network expires.

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

integration/utils.go

@@ -0,0 +1,48 @@
+package integration
+
+import (
+	"testing"
+)
+
+func pingAllHelper(t *testing.T, clients []TailscaleClient, addrs []string) int {
+	t.Helper()
+	success := 0
+
+	for _, client := range clients {
+		for _, addr := range addrs {
+			err := client.Ping(addr)
+			if err != nil {
+				t.Errorf("failed to ping %s from %s: %s", addr, client.Hostname(), err)
+			} else {
+				success++
+			}
+		}
+	}
+
+	return success
+}
+
+// pingAllNegativeHelper is intended to have 1 or more nodes timeing out from the ping,
+// it counts failures instead of successes.
+// func pingAllNegativeHelper(t *testing.T, clients []TailscaleClient, addrs []string) int {
+// 	t.Helper()
+// 	failures := 0
+//
+// 	timeout := 100
+// 	count := 3
+//
+// 	for _, client := range clients {
+// 		for _, addr := range addrs {
+// 			err := client.Ping(
+// 				addr,
+// 				tsic.WithPingTimeout(time.Duration(timeout)*time.Millisecond),
+// 				tsic.WithPingCount(count),
+// 			)
+// 			if err != nil {
+// 				failures++
+// 			}
+// 		}
+// 	}
+//
+// 	return failures
+// }