Update invirt-images to version 0.0.7

Requested by quentin/root@ATHENA.MIT.EDU

diff --git a/invirt-images b/invirt-images
index 91cbf1b..abe7309 160000 (submodule)
--- a/invirt-images
+++ b/invirt-images
@@ -1 +1 @@
-Subproject commit 91cbf1beadaade4ac71d07c0214fc382fb2090c3
+Subproject commit abe7309a4eb1d205eb0c8342423821ad2878695e