tests/avocado: apply proper skipUnless decorator

tests/avocado: apply proper skipUnless decorator

Commit 9b45cc993 added many cases of skipUnless for the sake of
organizing flaky tests.  But, Python decorators *must* follow what
they decorate, so the newlines added should *not* exist there.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Tested-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Message-ID: <20240806173119.582857-3-crosa@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>