Fix bogus bash binary location

plugins/available/nginx.plugins.bash

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 function nginx_reload() {
   FILE="${NGINX_PATH}/logs/nginx.pid"
@@ -47,4 +47,4 @@ function nginx_restart() {
     echo "Nginx pid file not found"
     return 0
   fi
-}
+}