Fix a bug where we didn't call IME before calling augmented autofill

* For inline autofill, we always need to get an IME callback before
  calling the augmented autofill service. This is because although
  autofill keeps a list of undestroyed sessions, the IME side
  always discards the old callback for autofill when a new one
  is created. So in case of switching back to an existing autofill
  session, we need to make sure we ask the IME to return a new
  callback.
* we current have the check which missed a case where we are
  re-entering an existing autofill session, but the standard
  autofill was returning null the previous time,
  so it goes to trigger augmented autofill directly. In this case,
  we need to call IME onCreateInlineSuggestionsRequest to get a
  callback before calling the augmented autofill. We didn't, and
  this patch fixes it.

Test: atest android.autofillservice.cts.inline
Test: manual
Bug: 158877106
Change-Id: Ie15cf0763ae49a204ad09c2eaac798890388622e