Grumble, apps should check features before using.

Turns out several apps are blindly grabbing a FINGERPRINT_SERVICE
reference without checking to see if the device actually includes
that feature.

Hand pre-O apps a stubbed out Manager instance, but keep the new
ServiceNotFoundException behavior intact going forward, since it
prevents race conditions during boot or Binder service restarts.

Test: builds, boots
Bug: 32566669
Change-Id: Id1c0873e98e59b255f32e0f9204f4525a345f9ef