SystemUI: fix visualizer tile initial state

If something was playing intially and the tile detected so via the cold
check, it would be eventually overridden by the checkIfPlaying() method
because it always assumed the initial state to be false, which is not
always so.

Change-Id: I32c0c358be1e9e64c7185ae5012f28bc1279cbf8
Signed-off-by: Roman Birg <roman@cyngn.com>