Merge ~d0ugal/maas-images:grub-common into maas-images:master

[Dougal Matthews]

Add the missing grub-common dep

Without this dep the following command fails when attempting to make a
subprocess call to grub-mkimage.
  meph2-util import --no-sign conf/bootloaders.yaml bootloaders.d

[Alberto Donato (ack)]

+1

review: Approve

diff --git a/system-setup b/system-setup
index 7410c2c..cc30b09 100755
--- a/system-setup
+++ b/system-setup
@@ -27,13 +27,14 @@ DEPS_UTIL_ONLY=(
 DEPS_FULL=(
     bzr
     cloud-image-utils      # for mount-image-callback
+    dpkg                   # To compare bootloader package versions
     gpgv
+    grub-common            # Used by the bootloaders
     python3-distro-info
     python3-requests
     python3-yaml
     squashfs-tools
     zerofree
-    dpkg                   # To compare bootloader package versions
 )
 
 apt_get() {