Improve test using Mockito.argThat() matcher

Instead of matching any() display, this CL uses argThat() matcher to
verify only for DEFAULT_DISPLAY.

Note that initializeDisplayManger() helper does nothing in those tests
because DisplayManager instance in NavigationBarController is already
initialized in @Before and can't be replaced with a mock.

Bug: 142293903
Test: atest SystemUITests:NavigationBarControllerTest
Change-Id: Ic203f06a9612681ca41025596800b320c2307c09