Make countStepExecutions access batch_job_execution only once

[marschall]

Change JdbcStepExecutionDao.COUNT_STEP_EXECUTIONS to access the table
batch_job_execution only once.

JdbcStepExecutionDao.COUNT_STEP_EXECUTIONS accesses batch_job_execution twice.

SELECT
    COUNT(*)
FROM
    batch_job_execution    je,
    batch_step_execution   se
WHERE
    se.job_execution_id IN (
        SELECT
            job_execution_id
        FROM
            batch_job_execution
        WHERE
            job_instance_id = ?
    )
    AND se.job_execution_id = je.job_execution_id
    AND se.step_name = ?;

there is no need for this, the query can be simlified to

SELECT
    COUNT(*)
FROM
         batch_job_execution je
    JOIN batch_step_execution se ON se.job_execution_id = je.job_execution_id
WHERE
        je.job_instance_id = ?
    AND se.step_name = ?;

[fmbenhassine]

LGTM. Rebased and merged as 9710220. Thank you for your contribution!