[Bug] decorator problem with MockAlgorithmClient method

[harmbuisman]

Describe the bug
When using the MockAlgorithmClient, the order of decorators of the called method leads to an error:
@algorithm_client
@DaTa()

KeyError: 'INPUT_FILE' as it tries to get INPUT_FILE from os.environment.

The following order however works:
@DaTa()
@algorithm_client

To Reproduce
you can reproduce it by setting the wrong order in the mock_page.init file in the preprocessing branch and run make test