[tests-only] Adjust logic for testing on OCIS or REVA

[phil-davis]

Description

Before this PR, when testing on REVA you have to define bothe environment variables TEST_OCIS and TEST_REVA - that is not such an obvious thing.

1. adjust the test logic so that if just TEST_REVA is defined, then all the appropriate test setup and teardown happens.

2. change the environment variable TEST_EXTERNAL_USER_BACKENDS to TEST_WITH_LDAP to better reflect what it does. The test suite uses this environment variable to know to create/delete users and groups on LDAP... (rather than with the provisioning API)

Note: TEST_OCIS is only documented in owncloud/ocis repo. And the use of that does not change.
TEST_REVA and TEST_EXTERNAL_USER_BACKENDS are only documented in cs3org/reva repo. That will be changed in the PR that bumps the core commit.
None of these are mentioned in owncloud/docs so there is nothing to change there!

I will make a PR in user_ldap repo to change TEST_EXTERNAL_USER_BACKENDS after this PR is merged.

After this PR, we want to adjust the logic in a separate PR so that user data and shares are not cleaned up "under-the-hood" when running on OCIS. There is an OCIS PR in development that will cleanup user files, shares and other metadata correctly when the user is deleted using the provisioning API.

How Has This Been Tested?

CI

PR cs3org/reva#1295 demonstrates that this works.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:
• Changelog item, see TEMPLATE

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

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[jasson99]

Looks good to me