image_build: accept Kiwi vagrant image name format

According to Neal, Vagrant images produced by Kiwi end in e.g.
`vagrant.libvirt.box` and `vagrant.virtualbox.box` - with a
period between `vagrant` and the image type, not a dash as with
oz. We should accept this slightly different format so we can
correctly derive the productmd `type` and `format` for these.

Signed-off-by: Adam Williamson <awilliam@redhat.com>
(cherry picked from commit 93b4b4ae0f)

pungi/phases/image_build.py

@@ -34,8 +34,8 @@ EXTENSIONS = {
     "rhevm-ova": ["rhevm.ova"],
     "tar-gz": ["tar.gz"],
     "vagrant-hyperv": ["vagrant-hyperv.box"],
-    "vagrant-libvirt": ["vagrant-libvirt.box"],
-    "vagrant-virtualbox": ["vagrant-virtualbox.box"],
+    "vagrant-libvirt": ["vagrant-libvirt.box", "vagrant.libvirt.box"],
+    "vagrant-virtualbox": ["vagrant-virtualbox.box", "vagrant.virtualbox.box"],
     "vagrant-vmware-fusion": ["vagrant-vmware-fusion.box"],
     "vdi": ["vdi"],
     "vmdk": ["vmdk"],