Ensure CryptKeeper runs with its own task affinity

- Otherwise, when it finishes and home is started in the same task,
  subsequent launches of Settings activities will be routed to the
  home task incorrectly.

Bug: 154890505
Bug: 150983816
Test: Flash & wipe device, finish SUW, launch a quick settings
      settings activity, ensure it starts in a new non-home task
Change-Id: I48db005a5c292f76ab23b34a194b209c6d1b2335