Add comment to clarify error handling intention

Signed-off-by: Jason T. Greene <jason.greene@redhat.com>

pkg/machine/pull.go

@@ -67,6 +67,7 @@ func NewGenericDownloader(vmType, vmName, pullPath string) (DistributionDownload
 func supportedURL(path string) (url *url2.URL) {
 	getURL, err := url2.Parse(path)
 	if err != nil {
+		// ignore error, probably not a URL, fallback & treat as file path
 		return nil
 	}