Fix locked second screen on boot

Before, when hid and showed a different keyguard presentation, the
onDismissListener would remove the newly added one, which caused the
later presentation existence check to return the incorrect value. Now,
we add a check to only remove the dismissed presentation.

Bug: 152253158
Test: MultiDisplayKeyguardTests#testUnlockScreen_secondDisplayChanged_dismissesKeyguardOnUnlock
      MultiDisplayKeyguardTests#testUnlockScreen_decoredSystemDisplayChanged_dismissesKeyguardOnUnlock
Change-Id: I9dabc15e1228cc9417ed24981b332b8f1af818c8