Account for race condition when attaching HDMI.

The status bar figures out how tall it needs to be by
subtracting 720 (for 720p HDMI output) from the display
height. However, if the display is in the process of
rotating to portrait when HDMI is attached (or for whatever
other reason dispatches the HDMI_PLUGGED_STATE before the
display has been rotated to landscape) this computation will
be wrong.

The quick fix is to compute the status bar height as
shortSide - 720 rather than height - 720.

Bug: 4284690
Change-Id: I3715264a9e32af1299777ccdbdc22ca60926cc79