useradd{-static}: Ignore useradds on nativesdk

The code was supposed to ignore both native and nativesdk operations when
using the useradd and useradd-static code.  However, somewhere along the way
the code was dropped.  This didn't cause any issues until someone enabled the
enforcing mode in the new useradd-static and various nativesdk packages
started to fail.

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>