classes/insane: do not leak host uid/gid into package_qa sstate signatures

classes/insane: do not leak host uid/gid into package_qa sstate signatures

This prevented package_qa sstate from being reusable unless host uid/gid
values would  match exactly (and they unfortunately do on the yocto autobuilder
worker machines which all share a 'pokybuild' user).

I noticed this when testing CDN sstate reuse, which otherwise works well.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>