Add genisoimage to package dependencies:

This package is required to boot instances with config_drive.

bug #1053304

Change-Id: Ib85220d17a73563d0af813d95b7de8fa95445ded
diff --git a/files/rpms/nova b/files/rpms/nova
index 568ee7f..7ff926b 100644
--- a/files/rpms/nova
+++ b/files/rpms/nova
@@ -3,6 +3,7 @@
 dnsmasq-utils # for dhcp_release
 ebtables
 gawk
+genisoimage # required for config_drive
 iptables
 iputils
 kpartx