NXCM1719UpdateSiteProxyIT: use localOnly when walking cached proxy content

Explicitly use the localOnly form of ResourceStoreRequest when walking the local content of proxy repositories.

NXCM1719UpdateSiteProxyIT is currently failing because after mirroring the remote content it walks the proxy repository with a `ResourceStoreRequest` that does not have `localOnly` set to `true` (as it was built using the single-argument constructor). This ends up causing the previously cached content to be removed, failing the IT.

I also fixed a couple of other places that looked like they could be called/used by proxy repositories and were using the single-argument `ResourceStoreRequest` constructor. But only the `UpdateSiteProxyRepositoryImpl` change is required to fix the failing IT.