Fixed errors found by staticcheck

Staticcheck has probably been updated and is finding new errors.
They have been fixed.

Also, moved the run of staticcheck before running the test suite,
so if it fails, it fails sooner ;-).

main.go

@@ -278,6 +278,9 @@ func configureClusterOpts(opts *server.Options) error {
 	// If cluster flag override, process it
 	if opts.Cluster.ListenStr != "" {
 		clusterURL, err := url.Parse(opts.Cluster.ListenStr)
+		if err != nil {
+			return err
+		}
 		h, p, err := net.SplitHostPort(clusterURL.Host)
 		if err != nil {
 			return err