[40network] Provide a hostname fallback function, in case there is no executable of this name

modules.d/40network/net-lib.sh

@@ -366,3 +366,7 @@ linkup() {
      && wait_for_if_up $1 2>/dev/null
 }
 
+type hostname >/dev/null 2>&1 || \
+hostname() {
+	cat /proc/sys/kernel/hostname
+}