SMB connection dialog, anonymous connections can be saved without checking the anonymous checkbox

[TranceLove]

Without entering username and/or password, user can still create/update a SMB connection to a public share. This makes the anonymous checkbox meaningless.

UI should

• block user from saving if username is not entered and anonymous checkbox is not checked
• disable username and password textfields if anonymous checkbox is checked
• allow save/update only when username is entered or anonymous checkbox is checked