Fix No Teardown on Failed Create Data Tests

[MRichards99]

Description:
On the ICAT backend, if any of the tests prefixed with test_valid in test_create_icat.py fail, the data that gets created from those tests won't get removed, thereby not leaving icatdb into a clean state once the tests have finished running. This happens because the data is removed at the end of the test function (after the assert statement) so any code after that won't run if it throws an AssertionError.

Acceptance criteria:

• All tests should still pass
• If any tests in test_create_icat.py with the test_valid prefix are provoked to fail, the investigations table on icatdb should still be in the same state that it started. This can be indirectly checked through the other tests - if it hasn't been fixed, there'll be lots of other test failures where investigation data is involved