[WIP] Hack to avoid Agent DN + Password being overwritten by some ugly browser...

...s with stored site credentials.

Fixes #7038

List of browsers having the bug. Checked ones are tested successfully against.

* [X] Chromium/Chrome
* [ ] Safari
* [ ] IE (11+)

Please review and test. Also open for better ideas.

@quiqueck @ser72 @PVince81 or others please