Add efi packages for ironic-agent

On IPA we are using efivar and efibootmgr, we already added the
packages on ipa-builder.
Adding the pacakges on diskimage-builder, so that people who use
it to build the images won't get into trouble.

Change-Id: I9ab6588f20302b4808b09dc060aced5fd267a3d2

diskimage_builder/elements/ironic-agent/package-installs.yaml

@@ -18,3 +18,5 @@ kmod:
 psmisc:
 dosfstools:
 mdadm:
+efibootmgr:
+efivar:

releasenotes/notes/add-efi-packages-70a19464d31ab8d7.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Adds `efibootmgr` and `efivar` packages to ironic-agent, so when building
+    DIB images they will be present.