Set divider hidden status after it update

If device is landscape then enter keygaurd, it will rotate to portrait
back but it does not handle previous hidden status so the divider will
show after it update.

Fix it by check hidden status before divider removed and set it after
divider added again.

Bug: 154862056
Test: enter split, rotate then screen off, enter keygaurd to check
      divider is hidden
Change-Id: If19bf9304c38ecee968aefba1b66f154701c5c09