Exclude finishing ActivityRecord when checking overlay

Before, we kept the untrusted mode embedded activity hidden even if the
overlay is finishing, which will not include the visible change in
the CLOSE transition. Now, we exculde the finishing overlay so that the
embedded activity visibility will be updated in the CLOSE transition.

Bug: 207070762
Test: atest CtsWindowManagerDeviceTestCases:TaskFragmentTrustedModeTest
Change-Id: I0056c4881623732a1671175b12ff1908dd3bcff6