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 triggers additional unnecessary remote fetching which ends up clearing the previously cached content, 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 strictly speaking only the `UpdateSiteProxyRepositoryImpl` change is required to fix the failing IT.