Account for DPM state when checking FLAG_SECURE

- If the profile has disable screen capture enabled on their work
  profile, then DPM service will directly set the secure state on
  the surfaces, but the window flags aren't updated. Callers need
  to check the cache state to also ensure that they report the
  right secure state when taking a snapshot and when rotating.

Bug: 156104186
Test: Open a work profile app with screen capture disabled and
      ensure the task snapshot dump state reflects the secure
      state
Change-Id: I7cc6d525c818346846d27bdfad1961b464dfb46d