Add "nss-lookup.target" and explanation why we want it

Signed-off-by: DL6ER <dl6er@dl6er.de>

advanced/pihole-FTL.service

@@ -1,6 +1,15 @@
 [Unit]
 Description=Pi-hole FTLDNS
+; This unit is supposed to indicate when network functionality is available, but it is only
+; very weakly defined what that is supposed to mean, with one exception: at shutdown, a unit
+; that is ordered after network.target will be stopped before the network
 After=network.target
+Requires=network.target
+; A target that should be used as synchronization point for all host/network name service lookups.
+; All services for which the availability of full host/network name resolution is essential should
+; be ordered after this target, but not pull it in.
+Wants=nss-lookup.target
+Before=nss-lookup.target
 
 [Service]
 Restart=on-abnormal