Check if QQS shows player when updating height

The media session attached to the player may have changed since the last
time the QQS layout was switched. So, check if the QuickQSPanel is showing
a player when deciding how to update the height. Don't check the state
of the media session.

Fixes: 149503712
Test: play podcast, pause and dismiss app. Go to lock screen and swipe
down to see QuickQS. Verify that the panel is appropriately sized.

Change-Id: I1d6252a1ea09d6938fe1b5da6a4bee05b2ebc30c