Merge lp:~rcj/vmbuilder/jenkins_kvm into lp:~ubuntu-on-ec2/vmbuilder/jenkins_kvm

[Robert C Jennings]

builder: Force boot with initramfs on disco

The initramfs-less boot causes a panic on initial boot for disco.
This should send it back to grub to reboot with an initramfs,
but the builder image is invoked with -no-reboot on the kvm command
line so the initramfs-less boot mechanism results in a panic and
no recovery. Rather than change how we launch to remove -no-reboot
this patch alters the grub environment to boot the first time with
an initrd.

Setting the initrdfail=1 grub variable for the builder means
that we boot correctly on the first boot and find the rootfs.

[Francis Ginther (fginther)]

review: Approve

[Robert C Jennings (rcj)]

With this change the disco builder does boot in production and begin image customization.

[Cody Shepherd (codyshepherd)]

review: Approve

=== modified file 'templates/img-update.tmpl'
--- templates/img-update.tmpl	2019-04-18 22:19:04 +0000
+++ templates/img-update.tmpl	2019-04-25 15:24:32 +0000
@@ -296,6 +296,11 @@
 esac
 xchroot update-grub
 
+# Force boot with initramfs on disco
+if [ "$suite" == "disco" ] ; then
+	xchroot /usr/bin/grub-editenv /boot/grub/grubenv set initrdfail=1
+fi
+
 # builder requirements
 [ -e ${mp}/etc/resolvconf/resolv.conf.d/original ] &&
 	rm ${mp}/etc/resolvconf/resolv.conf.d/original