oniro-wic: refrain from populating slot B with a copy of slot A

This saves half of the space used by compressed disk artifacts.

I ran into the issue when creating grubenv recovery logic. To my surprise the execution flow ended up in the case where both slots are available and timestamp on the kernel is used to break the tie.

Signed-off-by: Zygmunt Krynicki zygmunt.krynicki@huawei.com