Minor autofill fixes.

- Removed unused arg from RemoteFillService.FillServiceCallbacks methods.
- Changed a FillUi error to WTF.
- Removed unused imports.
- Removed unused variables.
- Dump afm.mIdShowFillUi.

Bug: none
Test: atest CtsAutoFillServiceTestCases

Change-Id: I12784a1a5ffbe3b2ced5bdb27c5fd3716aa876ee