Improve printer installation on teacherlaptops

- Update printer list when connected via VPN
- Prevent printer removal, when logging in without a connection to the school network

roles/lmn_printer/templates/install-printers.sh.j2

@@ -2,6 +2,9 @@
 
 set -eu
 
+## Exit if first printserver is not reachable
+ping -c1 -W1 {{ printservers | first }} || exit 0
+
 printservers="{{ printservers | join(' ') }}"
 hostgroup="$(id -Gn "${HOSTNAME^^}$")"
 usergroup="$(id -Gn "${SUDO_USER}")"

roles/lmn_teacherlaptop/files/10-lmn-mount.sh

@@ -30,6 +30,7 @@ if [[ "$CONNECTION_ID" = "VPN-Schule" ]]; then
           -o "sec=krb5i,cruid=${USERID},user=${USERNAME},uid=${USERID},gid=${GROUPID},file_mode=0700,dir_mode=0700,mfsymlinks,nobrl,actimeo=600,cache=loose,echo_interval=10"
 	  echo "after mount" >&2
     mount --bind /srv/samba/schools/default-school/share "/lmn/media/${USERNAME}/share"
+    SUDO_USER=$USERNAME /usr/local/bin/install-printers.sh
   elif [[ "$NM_DISPATCHER_ACTION" = "pre-down" ]]; then
     # FIXME: Only umount server when Wireguard-Connection was the only connection to server.
     # Dirty fix (works only in fvs-IP-Range)