The attached patch addresses most of the FTP login related problems and is a replacement for the previous review request
https://git.reviewboard.kde.org/r/100873/. Here are all the changes in this patch:

- Show the "Remember password" checkbox even after the failure of the first login attempt. [Bug:258888]
- Always check for cached password before trying to login anonymously unless the "TryAnonymousLoginFirst"
  flag was set in kio_ftprc. [Bug: 99686, 143488, 124675]
- Avoid sending the "anonymous" username so it will not be used in the key used to store the password in kwallet.
- When a url contains a username, but the user chooses to login with a different username in the password dialog, 
  then use redirection to update the client of the change.
- Store password information in persistent storage if and only if the user checked the "Remember password" checkbox.

- Attempt to login with incorrect username and validate the "Remember password" is actually shown again.
- Corrected the username information from the password dialog to ensure the client is updated properly about the password change.
- Clicked on the "Remember password" to store password in persistent storage and retry logging into the same server at a later point.