quickboot: Disable quickboot by default

* We probably don't want to enable this by default on devices that have
  it because it is confusing to users attempting to shut down their
  phones.

Change-Id: I80eb946f93509cb3b32f6c790611597921b9c54a
(cherry picked from commit cc13e50917807b7a7d66279189f773489dbf0c0f)