Fix multistrap.conf

Remove xen-linux-system-3.2.0-4-amd64 package and add packages from
the wheezy-helper suite of apt.dev.grnet.gr

snf-image-host/multistrap.conf

@@ -17,7 +17,7 @@ unpack=true
 # the order of sections is not important.
 # the debootstrap option determines which repository
 # is used to calculate the list of Priority: required packages.
-debootstrap=Debian GRNet
+debootstrap=Debian GRNet Helper
 aptsources=Debian
 
 [Debian]
@@ -26,9 +26,17 @@ source=http://ftp.gr.debian.org/debian
 suite=wheezy
 
 [GRNet]
-packages=snf-image-helper ufsutils linux-image-3.2.0-4-amd64 xen-linux-system-3.2.0-4-amd64
+packages=snf-image-helper
 # Don't change the parameters below unless you really know what you are doing.
 # The /'s and the empty `componets' variable are needed when working with apt.
 source=http://apt.dev.grnet.gr/
 suite=wheezy/
 components=
+
+[Helper]
+packages=ufsutils linux-image-3.2.0-4-amd64
+# Don't change the parameters below unless you really know what you are doing.
+# The /'s and the empty `componets' variable are needed when working with apt.
+source=http://apt.dev.grnet.gr/
+suite=wheezy-helper/
+components=