config: Build qcow2 images for all eos products

This will allow adding them to osinfo-db for all the same personalities
that the ISOs are used for. Providing the OS in a qcow2 image is
superior to an ISO since it avoids the step of writing the raw image to
a qcow2 image that GNOME Boxes provides.

https://phabricator.endlessm.com/T35332

config/product/eos.ini

@@ -3,3 +3,6 @@
 [image]
 # Build ISOs
 iso = true
+
+# Build QEMU qcow2 image
+qcow2 = true