nativesdk: Handle chown/chgrp calls in nativesdk do_install tasks

We disable the useradd code for nativesdk targets since we don't support
postinstalls or multiple users in those cases. This means any usage
of chown/chgrp inside do_install tasks won't work and would have to be
conditional. Rather than require all recipes to do that, add intercepts
of the calls and map those to root/root user/groups. We can't just ignore
them as some calls are used to remove host contamination from the host
user ID so they need to be made, just as root.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>