Try smart umount as a simple solution (no credentials needed).

roles/lmn_vm/files/pam-umount.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/bash
+#
+# <umount>/usr/local/sbin/pam-umount.sh %(USER) %(USERUID) %(MNTPT)</umount>'
+
+set -eu
+
+LANG=C
+usr="$1"
+uid="$2"
+mtp="$3"
+
+lmuh="/lmn/media/$usr/home"
+lmus="/lmn/media/$usr/share"
+
+for VMname in $(sudo -u $usr XDG_RUNTIME_DIR="/run/user/$uid" \
+		     virsh list --state-running | grep running | awk '{print $2}'); do
+    sudo -u $usr XDG_RUNTIME_DIR="/run/user/$uid" virsh destroy $VMname || true
+    sleep 1
+done
+#killall -9 virtiofsd
+
+if [[ "$mtp" =~ "/srv/samba/schools" ]] ; then
+    N=0
+    mh=true
+    ms=true
+    mountpoint -q $lmuh || mh=false
+    mountpoint -q $lmus || ms=false
+    while [[ $N -lt 10 ]] && ([[ $mh = true ]] || [[ $ms = true ]]) ; do
+	if [[ $mh = true ]] ; then
+	    umount "$lmuh" && mh=false
+	fi
+	if [[ $ms = true ]] ; then
+	    umount "$lmus" && ms=false
+	fi
+	N=$((N + 1))
+	sleep 1
+    done
+    systemd-cat echo "Tried $N umount(s)."
+fi
+exec umount "$mtp"