installer-media: Exclude extensions from VM name
installer-media: Exclude extensions from VM name

When creating label/VM name from an unknown media, we simply use the
basename of the media filename. There is no point in taking the
extensions and it usually only makes the name longer and is unlikely to
be desired by users.

https://bugzilla.gnome.org/show_bug.cgi?id=690757

vbenes/gnome-boxes,vbenes/gnome-boxes