pkg/mesh: ensure persistent-keepalive set on nodes

A bug identified by @carlosrmendes caused nodes to ignore the
persistent-keepalive annotation.

xref: https://github.com/squat/kilo/issues/53#issuecomment-620945927

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

pkg/mesh/mesh.go

@@ -485,6 +485,7 @@ func (m *Mesh) handleLocal(n *Node) {
 		Leader:              n.Leader,
 		Location:            n.Location,
 		Name:                m.hostname,
+		PersistentKeepalive: n.PersistentKeepalive,
 		Subnet:              n.Subnet,
 		WireGuardIP:         m.wireGuardIP,
 	}