Make Ubuntu Vagrant box 40G. (LP: #1580596)

Vagrant images were previously put at 10G, but this was a regression
from Trusty, in which they were 40G.  This made it a tough sell for
users to upgrade if they were using a Ubuntu desktop experience.

This change does not impact disk usage as Vagrant with the virtualbox
provider dynamically allocates space with the VMDK.  On a test system,
the VMDK took up 1.1G of disk space according to df, and after
creating a 2G file in Vagrant, the VMDK grew to 3.1G.

Therefore, users who are running on a system with little free space will
not see adverse effects if they upgrade to a new vagrant image

debian/changelog

@@ -1,3 +1,9 @@
+livecd-rootfs (2.408.60) xenial; urgency=medium
+
+  * Increase Vagrant disk size from 10G to 40G (LP: #1580596)
+
+ -- Patrick Viafore <patrick.viafore@canonical.com>  Tue, 26 May 2020 09:45:46 -0500
+
 livecd-rootfs (2.408.59) xenial; urgency=medium
 
   * Backport snap preseed base support (LP: #1874834)

live-build/ubuntu-cpc/hooks.d/base/vagrant.binary

@@ -105,7 +105,7 @@ distro=$(chroot chroot lsb_release --id --short | tr [:upper:] [:lower:])
 # Get the VMDK in place
 prefix="${distro}-${suite}-${version}-cloudimg"
 vmdk_f="${box_d}/${prefix}.vmdk"
-create_vmdk ${derivative_img} ${vmdk_f}
+create_vmdk ${derivative_img} ${vmdk_f} 40960
 
 ####################################
 # Create the ConfigDrive