Return mouse back to camera on closing VGUI dialog

[nullsystem]

• Affected teammenu and classmenu, loadoutmenu didn't seemed to, but also edited it just for consistency
• Reproducable with Alt-F4, although that's the default keybind for closing the window on Windows + major DEs on Linux. But using non-default keybind/other DE/WM easily reproduce it.
• fixes #371