Prevent force showing system bars for TaskView

Update the condition of force showing system bars to check adjacent
tasks instead of checking multi-window windowing mode so it can
distinguish from TaskView.

Fix: 273495037
Test: atest TaskDisplayAreaTests DisplayPolicyTests InsetsPolicyTest
Change-Id: Ibc056d4ac1fae7aa82001d815090a5be2cb703e9
6 files changed