HDS enable db job service

[andponlin]

This PR will remove the older flag env-var HDS_STORAGE_TYPE and will now enable the new flag to enable the database-based Job storage system using HDS_JOBSERVICE_TYPE.

After merging this, restart the HDS system.

Next, test the job system;

1. Authenticate as a user
2. Navigate to the reports page
3. Run the "Package icon archive" report
4. Download the resultant report data
5. Unpack the .tgz and check it contains images (OK)

Run the following query;

SELECT COUNT(id) FROM job.job;

This should return > 0 rows to indicate the system is using the database to operate the job system.

[andponlin]

It would be best to investigate the issue #169 first.