Fix rfkill test logic

A lack of focus lead to accepting a review comment that ended up being broken:

• We have changed from a test to a command pipeline, we don't need the square brackets.
• We have inadvertently switched the logic - we expect disabling Bluetooth to fail at this point as it should already have been switched off.

Correct the logic.

Signed-off-by: Martyn Welch martyn.welch@collabora.com