extract-iso: Make use of OS variants
extract-iso: Make use of OS variants

Take the name of first variant as 'nie:title', if any.

https://bugzilla.gnome.org/show_bug.cgi?id=719512

hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker