Fix 5380695 Lockscreen transport control must reflect error state

When a RemoteControlClient reports an error for its playstate,
 make the play/pause button display the warning platform icon.

Note that a specific image description is not available for this
 state at this time, but the one being used (the same as for the
 play icon) is valid as it correctly describes the action the
 button performs.

Change-Id: I59aadab3fe5bcc09a2f7be0b9e4cffb0c500e865