Cleanup on aborting auto-enter-pip

Note that this change does not fix the bug listed here. This is to
ensure WMShell can cleanup its internal state when the bug happens to
avoid further confusions in WMShell.

Bug: 283177443
Test: adb shell dumpsys activity service SystemUIService WMShell
Test: go/winscope and check the SF/WM dump
Change-Id: I3804d57458a20f6a1c41963a704fae8bb28f0392