libnet: Return proper error when overlay network can't be created

The commit befff0e13f68d39fed40e9f81bafc25042e944da inadvertendly
disabled the error returned when trying to create an overlay network on
a node which is not part of a Swarm cluster.

Since commit e3708a89ccf5c88273660b2409e2ea1197530b0b the overlay
netdriver returns the error: `no VNI provided`.

This commit reinstate the original error message by checking if the node
is a manager before calling libnetwork's `controller.NewNetwork()`.

Signed-off-by: Albin Kerouanton <albinker@gmail.com>
(cherry picked from commit 21dcbada2d1383ccf771410048cb1574dfe43c6d)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/network.go

@@ -291,6 +291,16 @@ func (daemon *Daemon) createNetwork(create types.NetworkCreateRequest, id string
 		return nil, PredefinedNetworkError(create.Name)
 	}
 
+	c := daemon.netController
+	driver := create.Driver
+	if driver == "" {
+		driver = c.Config().DefaultDriver
+	}
+
+	if driver == "overlay" && !daemon.cluster.IsManager() && !agent {
+		return nil, errors.New(`This node is not a swarm manager. Use "docker swarm init" or "docker swarm join" to connect this node to swarm and try again.`)
+	}
+
 	var warning string
 	nw, err := daemon.GetNetworkByName(create.Name)
 	if err != nil {
@@ -309,12 +319,6 @@ func (daemon *Daemon) createNetwork(create types.NetworkCreateRequest, id string
 		warning = fmt.Sprintf("Network with name %s (id : %s) already exists", nw.Name(), nw.ID())
 	}
 
-	c := daemon.netController
-	driver := create.Driver
-	if driver == "" {
-		driver = c.Config().DefaultDriver
-	}
-
 	networkOptions := make(map[string]string)
 	for k, v := range create.Options {
 		networkOptions[k] = v
@@ -373,10 +377,6 @@ func (daemon *Daemon) createNetwork(create types.NetworkCreateRequest, id string
 
 	n, err := c.NewNetwork(driver, create.Name, id, nwOptions...)
 	if err != nil {
-		if errors.Is(err, libnetwork.ErrDataStoreNotInitialized) {
-			//nolint: revive
-			return nil, errors.New(`This node is not a swarm manager. Use "docker swarm init" or "docker swarm join" to connect this node to swarm and try again.`)
-		}
 		return nil, err
 	}