Merge pull request #1244 from dotcloud/1020_add_variable

*Runtime: Add container=lxc in default env

container.go

@@ -641,6 +641,7 @@ func (container *Container) Start(hostConfig *HostConfig) error {
 	params = append(params,
 		"-e", "HOME=/",
 		"-e", "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
+		"-e", "container=lxc",
 	)
 
 	for _, elem := range container.Config.Env {