Correct position of divider bar when get display insets

The visibility of the navigation bar is invisible when the keyguard
is unlocked. The insets are not correct when invoked the
getDisplayInsets() to calculate the position of the divider bar. This
CL uses the getInsetsIgnoringVisibility() to get insets no matter the
visibility of the system bar.

Bug: 278521469
Test: Pre-condition : 1. Turn on auto rotate  2. 3-button navigation
       1. Create the split.
       2. Turn off screen
       3. Rotate to landscape
       4. Turn screen on
       5. Unlock the keyguard
Change-Id: Iecb06d4dd652dac4f44fe0ec90e196974114aacb