refactor(scripts): Structure code as per codestyle

Fix #1636
Refactor code according to code style
Constants, Functions, Script

scripts/wireguard/clientSTAT.sh

@@ -1,17 +1,14 @@
 #!/bin/bash
 # PiVPN: client status script
 
+### Constants
 CLIENTS_FILE="/etc/wireguard/configs/clients.txt"
 
+### Functions
 err() {
   echo "[$(date +'%Y-%m-%dT%H:%M:%S%z')]: $*" >&2
 }
 
-if [[ ! -s "${CLIENTS_FILE}" ]]; then
-  err "::: There are no clients to list"
-  exit 0
-fi
-
 scriptusage() {
   echo "::: List any connected clients to the server"
   echo ":::"
@@ -83,6 +80,12 @@ listClients() {
   grep '\[disabled\] ### begin' wg0.conf | sed 's/#//g; s/begin//'
 }
 
+### Script
+if [[ ! -s "${CLIENTS_FILE}" ]]; then
+  err "::: There are no clients to list"
+  exit 0
+fi
+
 if [[ "$#" -eq 0 ]]; then
   HR=1
   listClients