Rename ZookeeperLauncherCommand to ZooKeeperLauncherCommand.
Launch MongoDB server.

Add MongoDBLauncher actor which manages the lifecycle of MongoDB server.
Override Actor lifecycle methods to launch and shutdown server.

The lifecycle of the underlying server is always the same as that of its actor.
So there is no need for separate Launch or Shutdown messages.
Use time unit seconds in timeout value.

It is more readable to use time units such as seconds in timeout value.