Geo: Repository dedup should work on secondary too

In gitaly#1410 (closed) we defined two iterations where the first one is to fix the dedup + Geo conjunction and the second one is to get the dedup feature work on Geo secondary node. This issue materializes the second iteration. By the time of creating this issue, we don't know how to implement it but it's clear that we want dedup feature working on Geo secondary node too. See some suggestions in gitaly#1410 (closed)