ANDROID: fuse: Don't use readdirplus w/ nodeid 0

If we have a nodeid of 0, we've probably got a backing inode, and a
regular getattr will be fast. Otherwise, userspace is likely ill suited
to properly handle a readdirplus anyways.

Test: fuse_test
Bug: 219958836
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Change-Id: I02f031d87dcc5fcbe1e080e4f8ec92187b00fe2d