interal/resource/http: clear CA compression on rewrite

CAs are re-written into the fetched config as a base64 string to allow
cached reads to not require an additional fetch. When compression
support was added during the resource consolidation refactor for the
3.1.0 spec this interaction was missed.

The blackbox tests did not catch this as they were always clearing the
config cache on each run.

internal/resource/http.go

@@ -212,6 +212,8 @@ func (f *Fetcher) RewriteCAsWithDataUrls(cas []types.Resource) error {
 
 		encoded := dataurl.EncodeBytes(blob)
 		cas[i].Source = &encoded
+		// the rewrite wipes the compression
+		cas[i].Compression = nil
 	}
 	return nil
 }