Clean up rkpd client in keystore2

1. Remove helper functions for binders. Just do the work in the binder
   function (reducing layers).
2. Stop returning Result from new_native_binder. Those functions have
   no failure paths.
3. Add some debug logs

Test: keytore2_test
Change-Id: I99aeeefec1e39891a124e1eb02f5a19f7188ca76
1 file changed