Fix unpinning on device with Navigation Bar

The introduction of the long press back to kill option
messed with the stock behavior of the long press back
button to unpin the locked app. Fortunately, all the job
was already done for the no navigation bar case, so all I
did was to extend the same logic to the case where nav bar
is present.

Change-Id: I2921c653c6e9ce51d49bda31f6e9b64654aeaeaa