Disabling status bar & navbar assertions in tests

Disabling OpenAppColdTest, OpenAppWarmTest, CloseImeAutoOpenWindowToHomeTest and CloseImeWindowToHomeTest assertions regarding nav bar and status bar always visible as seems to be failing.

Bug: b/12912591 b/12912587
Test: atest FlickerTests:CloseImeWindowToHomeTest FlickerTests:CloseImeAutoOpenWindowToHomeTest FlickerTests:OpenAppColdTest FlickerTests:OpenAppWarmTest
Change-Id: I87c3d8270072a2039ea530a31a17f01aa70daeff