Fix reading attributes for playback restrictions

Playback restrictions can be lifted with the correct flag,
  FLAG_BYPASS_INTERRUPTION_POLICY, but this flag is for the
  system only. As such, it must be read by querying "all
  the flags" with AudioAttributes.getAllFlags() which is a
  system API which returns all the system flags. getFlags()
  only returns the public SDK flags.

Bug 19407114

Change-Id: I22dadfaf5d1b48b3c0754e1e6af00b734d790fec