Make ProjectUpdateActionsIntegrationTest more robust

[katmatt]

One of our integration tests failed with the following error:

FAILURE! - in io.sphere.sdk.sequencegenerators.BigIntegerNumberGeneratorIntegrationTest
checkNumbersBiggerThanLongMax(io.sphere.sdk.sequencegenerators.BigIntegerNumberGeneratorIntegrationTest)  Time elapsed: 1.252 sec  <<< FAILURE!
java.lang.AssertionError: 
[tests will fail if the project has not the correct language settings] 
Expecting:
 <["fr-FR"]>
to contain:
 <["de", "de-AT", "en"]>
but could not find:
 <["de", "de-AT", "en"]>

And this can happen when the ProjectUpdateActionsIntegrationTest fails, because it changes the project locale to FR.
We should make sure that this test rolls back all changes it does, so that it easier to find the root cause.