Add oldDream to mPreviousDreams always when dreams overlap

Bug: 270178573
Test: start dream; press power button; wake up device; start dream;
      ensure dream starts
Change-Id: Ie601d2b4303340f89001265ba685ae97ee7fd6d8
(cherry picked from commit 01c6a7af31831601d6affddeae5ddef44336630e)
1 file changed