Preserve repos between stage2 and stage3

This will add to the image size and push/pull times, but it saves from
having to do an eix-sync for each stage3 build and it lets the image
preserve the local crossdev repo which can't easily be regenerated.

Containerfile

@@ -15,5 +15,3 @@ RUN emerge -v --update --deep --newuse --with-bdeps=y @world
 
 # Configure the stage
 RUN puppet agent --test --runtimeout 0; [ $? -eq 2 ]
-
-RUN rm -rf /var/db/repos