Fix a fairly obvious logic error

Creation of sharded/replicated clients was swapped, sigh.

clientutil/backend.go

@@ -48,7 +48,7 @@ func NewBackend(config *BackendConfig) (Backend, error) {
 		}
 	}
 
-	if config.Sharded {
+	if !config.Sharded {
 		return &replicatedClient{
 			u: u,
 			c: newHTTPClient(u, tlsConfig),