How to set user in ContainerLaunchContext?

[Peter Rudenko]

Hi, i have an ApplicationMaster which accepts requests and launches 
spark jobs. In request i have a field "username" - the user i want to 
laucnh a job from. How can i set a user which will be run conmmand on a 
container? Currently they all running as yarn user even though AM is 
running as a root user.

Thanks,
Peter Rudenko