fix: Always use `dpkg-divert` instead of altering files maintained by packages

Altering a file maintained by a package can lead to unexpected behaviou expecially in
this case where packages are being removed and added.

Instead use `dpkg-divert` to allow us to mock `lxd` to `true` to allow `unminimize` to work
without error and to avoid installing of the `lxd` snap.

live-build/ubuntu-server/hooks/01-unminimize.chroot_early

@@ -15,11 +15,16 @@ esac
 # We can't do that at this stage so just neuter the lxd command (the snap
 # will get properly seeded by generic machinery).
 if [ -f "/usr/sbin/lxd" ]; then
-    rm --verbose --force /usr/sbin/lxd
+    dpkg-divert --add --divert /usr/sbin/lxd.REAL --rename /usr/sbin/lxd
     ln -s /bin/true /usr/sbin/lxd
     yes | /usr/local/sbin/unminimize
     # unminimize also uninstalls lxd-installer package
-    # and also removed `/usr/sbin/lxd` as a result so we don't need to restore
+    # and also removed `/usr/sbin/lxd` as a result, so we don't need to restore, but
+    # we do need to remove the mock we used as part of dpkg-divert
+    # first we need to remove the diversion
+    dpkg-divert --remove --no-rename /usr/sbin/lxd
+    # now remove the renamed file that we originally diverted to
+    rm -v /usr/sbin/lxd.REAL
 else
     # if /usr/sbin/lxd doesn't exist then lxd-installer package isn't installed.
     # Instead, we can mock the command to avoid the unminimize script failing