UI - Add password fill compatiblity for "connectToServer" (2.19+)

[veteran29]

When merged this pull request will:

• title
• Info from @dedmen

https://github.com/CBATeam/CBA_A3/blob/master/addons/ui/fnc_initDisplayPassword.sqf#L6
`_targetServer = _display getVariable "guid"; // 127.0.0.1:2302 always the resolved IP address, not the domain`
Starting with next week dev, and profiling branch v20
The variable is set before the init event, it should always be present

`diag_log [_display, _display getVariable ["guid", "?"]];`
`11:39:47 [Display #64,"164.152.123.222:2331"]`