Capture real snapshot of task for non cache case

The caller should be responsible to use the snapshot for proper cases.
E.g. one time animation.

For the caller related to recents app list, they are using
updateCache=true, so the standard snapshot policy (exclude secure
or disable-recent) is still followed.

Fix: 308881017
Fix: 309111443
Test: Invoke takeTaskSnapshot for a task with an activity
      uses setRecentsScreenshotEnabled(false)
Change-Id: I1410e64485755428f7431a1529a3d5e385c48796