ec2-batch-job script fixes

In order to make ec2-batch-job on part with fargate-batch-job:
1) exec_ec2.sh: Change from "fargate-batch-job" to "ec2-batch-job".
2) cleanup_ec2.sh: Copy cleanup.sh to cleanup_ec2.sh. Change from "fargate-batch-job" to "ec2-batch-job".

I am making and fixing the issue in my fork first.

Start by comparing exec_ec2.sh and cleanup.sh with the corresponding fargate-batch-job scripts. Create or update cleanup_ec2.sh from cleanup.sh and verify that both EC2 scripts use the ec2-batch-job name, matching the requested parity with Fargate.

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