device policy: ignore unknown permission in setPermissionGrantState

When setting a permission grant on a non-existent permission,
implementation currently throws RemoteException but that's not
propagated across binder causing the client cide to stuck until
the timeout. Replace this with an immediate fail.

Bug: 197200931
Test: manual with TestDPC
Change-Id: I9a0ea42e52d68259eb0464194a5a1d9fbfc2a216