Serve latest version of plugin resources when cache is stale

When serving HTTP plugin resources from cache,
we do need to check the cached lastModifiedDate
against the underlying plugin entry latest update.

If dates do not match, we need to fetch again the
entry and return it back to the client, updating
the in-memory cache.

Without this fix, the in-memory cached copy was
always returned even if the one on the file-system
was actually updated.

Change-Id: I36ee9989ade0640fb5ceda73749efb852d6c5801
3 files changed