Fix tests

[tramora]

Fix broken tests.

When a remote access test (s3, gcs) fails it leaves the env variables dirty. This impacts the subsequent tests.
The cleaning cannot be done in a decorator because the execution flow is interrupted when the test fails. The best place for the cleaning is into the tearDown method.

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[popescu-v]

See the comments. Also copy the PR description to the commit message of the main commit of this PR.

[tramora]

See the comments. Also copy the PR description to the commit message of the main commit of this PR.
the test was improved and the commit message also.

[popescu-v]

LGTM