MT#62436 Prevent vboxadd* services to run outside of VirtualBox envs

We get failing ngcp-status on our trunk systems, due to:

| root@spce:~# systemctl --failed
|   UNIT                    LOAD   ACTIVE SUB    DESCRIPTION
| ● vboxadd-service.service loaded failed failed VirtualBox Guest Additions Services Daemon
| ● vboxadd.service         loaded failed failed vboxadd.service

While we're not even running inside a VirtualBox environment:

| root@spce:~# systemd-detect-virt
| kvm

We install /etc/systemd/system/vboxadd-service.service.d/override.conf
and /etc/systemd/system/vboxadd-service.service.d/override.conf with
`ConditionVirtualization=oracle` through our templates (see its git rev
a2521b609300965e5f8dfdeee63c5961f2d6a559) to address this. But this is
too late to the party, as the vboxadd* services are started *before* our
overrides get relevant.

So ensure we place the overrides already *before* even installing the
VBoxGuestAdditions.iso and executing its VBoxLinuxAdditions.run.

This then prevents the execution inside our Proxmox VMs, and not
reporting failing vboxadd-service + vboxadd services then:

| systemd[1]: vboxadd.service was skipped because of an unmet condition check (ConditionVirtualization=oracle).

Change-Id: I1a3a04bdc5d92d3fc79b336018ac5f588266c59b
(cherry picked from commit e2db6df5d0)

templates/scripts/includes/deployment.sh

@@ -1065,6 +1065,23 @@ EOF
   fi
 }
 
+vbox_adjust_vboxadd_service() {
+  mkdir -p "${TARGET}"/etc/systemd/system/vboxadd.service.d
+  mkdir -p "${TARGET}"/etc/systemd/system/vboxadd-service.service.d
+
+  cat > "${TARGET}"/etc/systemd/system/vboxadd.service.d/override.conf << EOF
+# deployed via deployment-iso's deployment.sh
+[Unit]
+ConditionVirtualization=oracle
+EOF
+
+  cat > "${TARGET}"/etc/systemd/system/vboxadd-service.service.d/override.conf << EOF
+# deployed via deployment-iso's deployment.sh
+[Unit]
+ConditionVirtualization=oracle
+EOF
+}
+
 vagrant_configuration() {
   # bzip2, linux-headers-amd64 and make are required for VirtualBox Guest Additions installer
   # less + sudo are required for Vagrant itself
@@ -1136,6 +1153,9 @@ vagrant_configuration() {
     die "Error: could not find $vbox_isofile"
   fi
 
+  # ensure we don't try to run vbox* services outside of VirtualBox environments
+  vbox_adjust_vboxadd_service
+
   mkdir -p "${TARGET}/media/cdrom"
   mountpoint "${TARGET}/media/cdrom" >/dev/null && umount "${TARGET}/media/cdrom"
   mount -t iso9660 "${vbox_isofile}" "${TARGET}/media/cdrom/"