[tests-only] Save exitcode of last occ command

Description

The PR https://github.com/owncloud/core/pull/40359 has implemented different method to save the exitcode of the last occ command and the local tests were failing because the exitcode was not saved. In this PR, I have implemented the updated way to save the occ exitCode.

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

[ ] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

[ ] My code follows the code style of this project.
[ ] My change requires a change to the documentation.
[ ] I have updated the documentation accordingly.
[ ] I have read the CONTRIBUTING document.
[ ] I have added tests to cover my changes.
[ ] All new and existing tests passed.

owncloud / data_exporter

[tests-only] Save exitcode of last occ command #213