Do not update etc/hosts for every container

- Only user named containers will be published into
  other containers' etc/hosts file.
- Also block linking to containers which are not
  connected to the default network

Signed-off-by: Alessandro Boch <aboch@docker.com>

daemon/network/settings.go

@@ -43,4 +43,5 @@ type Settings struct {
 	SandboxKey             string
 	SecondaryIPAddresses   []Address
 	SecondaryIPv6Addresses []Address
+	IsAnonymousEndpoint    bool
 }