Refine warning for storing registry passwords

This change refines the warning message returned during docker login to
only warn for unencrypted storage when the users password is being stored.
If the remote registry supports identity tokens, omit the warning,
since those tokens can be independently managed and revoked.

Signed-off-by: Daniel Hiltgen <daniel.hiltgen@docker.com>

cli/command/registry/login.go

@@ -143,7 +143,8 @@ func runLogin(dockerCli command.Cli, opts loginOptions) error { //nolint: gocycl
 	creds := dockerCli.ConfigFile().GetCredentialsStore(serverAddress)
 
 	store, isDefault := creds.(isFileStore)
-	if isDefault {
+	// Display a warning if we're storing the users password (not a token)
+	if isDefault && authConfig.Password != "" {
 		err = displayUnencryptedWarning(dockerCli, store.GetFilename())
 		if err != nil {
 			return err