Fix #1627402: fix grub2 element for ubuntu xenial

Looks that the special handling for Ubuntu is not needed any longer
(its a pity that there are no detailed comments...).

The grub2 element is a second implementation of the bootstrap element
- but because there are some features that come only here, e.g. efi
boot, it should be working as long as this is not implemented in the
bootloader element.

Change-Id: I74269116ea30b84f3259805720d5cd1616f960c5
Signed-off-by: Andreas Florath <andreas@florath.net>
Closes-Bug: #1627402

diskimage_builder/elements/grub2/install.d/02-grub-install-spec

@@ -1,19 +0,0 @@
-#!/bin/bash
-
-if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
-    set -x
-fi
-set -eu
-set -o pipefail
-
-# grub-efi-amd64-signed in ubuntu post will try to call grub-efi-amd64 to install grub into root
-# device which definitely fail at this stage
-# the workaround is to skip error and remove postinst script
-if [[ "ubuntu" =~ "$DISTRO_NAME" ]]; then
-    if ! install-packages grub-efi-amd64-signed; then
-        rm -f /var/lib/dpkg/info/grub-efi-amd64-signed.postinst
-        rm -f /var/lib/dpkg/info/grub-efi-amd64.postinst
-    fi
-    dpkg --configure grub-efi-amd64
-    dpkg --configure grub-efi-amd64-signed
-fi

diskimage_builder/elements/grub2/pkg-map

@@ -1,11 +1,4 @@
 {
-  "distro":{
-    "ubuntu":{
-      "signed_grub_efi": "",
-      "signed_shim_efi": "shim-signed",
-      "grub_bios": "grub-pc-bin"
-    }
-  },
   "family":{
     "debian":{
       "signed_grub_efi": "grub-efi-amd64-signed",