Add genisoimage to package dependencies:

This package is required to boot instances with config_drive.

bug #1053304

Change-Id: Ib85220d17a73563d0af813d95b7de8fa95445ded
diff --git a/files/apts/nova b/files/apts/nova
index ba6d8c5..f4615c4 100644
--- a/files/apts/nova
+++ b/files/apts/nova
@@ -18,6 +18,7 @@
 libjs-jquery-tablesorter # Needed for coverage html reports
 vlan
 curl
+genisoimage # required for config_drive
 rabbitmq-server # NOPRIME
 qpidd # dist:precise NOPRIME
 socat # used by ajaxterm