Conditionally show bootanimation for quiescent boots

Allow bootanimation to play if the boot is quiescent and the system
property ro.bootanim.quiescent.enabled is set to true.
This allows the bootanimation to become visible if the display is
turned on during the bootanimation. If OEMs want this behavior and the
device implements suppression of video/audio during quiescent boot,
they can set the system property
ro.bootanim.quiescent.enabled.

Bug: 185118020
Test: PRODUCT_PRODUCT_PROPERTIES += ro.bootanim.quiescent.enabled=true
      adb reboot quiescent
      Spam `adb shell input keyevent POWER` during boot
Test: Repeat the above test with the property set to 0
Change-Id: I54a4ad552704106ca06c4992fed4a2d501aa3fa5