Fix setSystemBarsAppearances

We should compare the existing appearance with the new appearance which
is about to be applied to insetsFlags.appearance, not the raw appearance
from the argument, before deciding if we can skip it.

Bug: 224613946
Fix: 226227461
Test: atest WindowInsetsControllerTests#testSetSystemBarsAppearance
Change-Id: I1283089a3dadf4ca2c3136f80d1472a34351306a