No status bar for external display

The test cases were failed to get the VR display because the
height of newly created display doesn’t match the expected
size. We shouldn’t remove status bar size from the display’s
height since there is no status bar on VR display (not even
on any external displays yet).

Bug: 117894098
Test: atest ActivityManagerVrDisplayTests
Change-Id: If053d3102cfadf511f1065f6475f37468e1d1836