controller: don't try to set integrity on XP x64 edition
controller: don't try to set integrity on XP x64 edition

XP x64 uses version 5.2, but doesn't accept setting the pipe to low
integrity.

5.2 seems to be shared with many versions (server 2003 for example),
but only Vista+ matters, which is only major >=6.

https://bugzilla.redhat.com/show_bug.cgi?id=918342

freedesktop-unofficial-mirror/spice__spice-gtk,flexVDI/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,elmarco/spice-gtk,elmarco/spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,SPICE/spice-gtk,Fantu/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,Fantu/spice-gtk,elmarco/spice-gtk,SPICE/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,guodong/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,fgouget/spice-gtk,guodong/spice-gtk,guodong/spice-gtk,elmarco/spice-gtk,flexVDI/spice-gtk