pkg/{k8s,mesh}: introduce liveness checks

This commit introduces liveness checks to Kilo. This allows the Kilo
daemons to take nodes with inactive or dead Kilo deamons out of the
topology until they are alive again.

pkg/mesh/mesh_test.go

@@ -17,6 +17,7 @@ package mesh
 import (
 	"net"
 	"testing"
+	"time"
 )
 
 func TestNewAllocator(t *testing.T) {
@@ -133,6 +134,7 @@ func TestReady(t *testing.T) {
 				ExternalIP: externalIP,
 				InternalIP: internalIP,
 				Key:        []byte{},
+				LastSeen:   time.Now().Unix(),
 				Subnet:     &net.IPNet{IP: net.ParseIP("10.2.0.0"), Mask: net.CIDRMask(16, 32)},
 			},
 			ready: true,