libbinder_ndk: Fix 'isRemote' value for Bn*.

Bn* is not remote (it's local).

This wasn't noticed before since the AIDL generated method 'associate'
always wrapped a proxy, and since a wrapped Bn object will always have
a null remoteBinder, it would properly show that it was local even
though it was wrapped.

Bug: 127336441
Test: atest android.binder.cts
Change-Id: Ic4d96822a355e88bc8f3dbbc8fa602835653139e