Fix main stage full screen after lock phone

We will set main stage to full screen when it visible but side
stage not visible, but we should not do it when phone unlock.
Add isSleeping check to avoid such problem.

Fix: 193605614
Test: pick any 2 apps to stage split then lock and unlock phone.
Change-Id: I0fd99960ca0c5a10ac33b23f92f01d9b48877379