[Job Debugging] An option for user to enable debugging reservation

[ydye]

What would you like to be added:

when submitting the job, user can specify the the optional flag in the jobEnv. 

If the flag is true and the job failed due to users' error, the job container will be reserved. 
Or the container will directly exit. 

Why is this needed:

1. If all container will be reserved in OpenPAI, much of the resource will be wasted. So the default behavior should be false.
2. Not all of users has the demand to debug the failed job.

Without this feature, how does the current module work：

Unable to directly exit from a failed container due to users' error.

Components that may involve changes:

Restserver