[TASK] Skip tests that rely on internet connection

Some tests in GeneralUtilityTest rely on a working internet
connection and fail if offline. Skip those tests if no needed.

Change-Id: Ia5e828cee6a834b971ad8d9c7da0598867a275f8
Resolves: #51496
Releases: 6.2
Reviewed-on: https://review.typo3.org/23445
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn