libbinder: ignore CallRestriction for magic 0 cmd

There is a special transaction required to make sure that the context
manager is setup before we get a reference to it. Since this is required
to use binder, it would prevent use of CallRestriction outside of
servicemanager.

Fixes: 167302413
Test: binderLibTest

Change-Id: I029e2a99013008a7c8614d63dc29df2889067d11