Clear more session values on impersonate

[PVince81]

Clear "app_password" and "loginname" after impersonate as it could cause side effects.

Or better would be if we could generate a new session id and set our vars there, then go back to the old session. We'd need to store the session id in the new session to be able to go back to the old session.

If that is not possible, then we need to relogin as the admin but we'll then lose the values like "app_password" and "loginname".

@butonic @DeepDiver1975 @sharidas @Peter-Prochaska