Farewell PID one

This change no longer runs Docker as PID 1.  Instead PID 1 is a very
simple zombie reaper and Docker is moved as a child of that PID.

config/types.go

@@ -101,6 +101,7 @@ type DockerConfig struct {
 	CAKey          string   `yaml:"ca_key,omitempty"`
 	Environment    []string `yaml:"environment,omitempty"`
 	StorageContext string   `yaml:"storage_context,omitempty"`
+	Exec           bool     `yaml:"exec,omitempty"`
 }
 
 type StateConfig struct {