lxd: Install some important packages

These packages with a priority of "important" are normally included as
part of base Debian installs. This only affects new containers.

Without apt-utils, a warning can be seen when installing packages:
debconf: delaying package configuration, since apt-utils is not installed

By default Debian installs whiptail rather than dialog.

Change-Id: Id94a4ba1702daa02db9de8744211f2b1ae518d87
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/containers/cros-container-guest-tools/+/3614209
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: James Ye <jamesye@google.com>
Reviewed-by: Fergus Dall <sidereal@google.com>
diff --git a/lxd/debian.yaml b/lxd/debian.yaml
index 0b692d7..a02f878 100644
--- a/lxd/debian.yaml
+++ b/lxd/debian.yaml
@@ -155,7 +155,8 @@
   cleanup: true
   sets:
   - packages:
-    - dialog
+    - apt-utils
+    - cpio
     - ifupdown
     - init
     - iproute2
@@ -169,6 +170,7 @@
     - procps
     - sudo
     - vim
+    - whiptail
     action: install
   # python3 is used for integration testing.
   - packages: