Description

Bareos used to reserve the devices very early, even before the run before job scripts.
When the scripts are used to e.g. create a database dump which takes a very long time,
the storage device is blocked while no data is being written.

This PR makes sure devices are reserved at the latest time possible before starting the physical writing.

Please check

• Short description and the purpose of this PR is present above this paragraph
• Your name is present in the AUTHORS file (optional)

If you have any questions or problems, please give a comment in the PR.

Helpful documentation and best practices

• Git Workflow
• Automatic Sourcecode Formatting
• Check your commit messages

Checklist for the reviewer of the PR (will be processed by the Bareos team)

General

• PR name is meaningful
• Purpose of the PR is understood
• Commit descriptions are understandable and well formatted
• Check backport line
• Is the PR title usable as CHANGELOG entry?
• Separate commit for CHANGELOG.md ("update CHANGELOG.md"). The PR number is correct.

Source code quality

• Source code changes are understandable
• Variable and function names are meaningful
• Code comments are correct (logically and spelling)
• Required documentation changes are present and part of the PR
• bareos-check-sources --since-merge does not report any problems

Tests

• Decision taken that a test is required (if not, then remove this paragraph)
• The choice of the type of test (unit test or systemtest) is reasonable
• Testname matches exactly what is being tested
• On a fail, output of the test leads quickly to the origin of the fault