Fix a potential crash when calculate system gesture exclusion

When calculate the exclude region during the swipe gesture. There is a
chance to meet index out of bounds exception when traverse all windows
to assemble the gesture exclusion rects. We add a WM lock to protect
the window state correctly.

Bug: 135298121
Test: atest DisplayPolicyTests
      atest DisplayContentTests

Change-Id: Ib71134d97e43ac91ce6713dd3dbf30280c44c574
(cherry picked from commit 3cf3e56a)