Fix various issues with loading os definitions (#11640)

* Ping only device doesn't display
if os was set to something, ping os wasn't loaded and we try to get overview graphs from it.

* Fix snmp_disable device page load error
When other os is set.

* Revamp os setting loading
the only safe way to access is Config::getOsSetting()

* Remove getOsSetting fallback behavior
Most instances don't use it and it can have unexpected results Config::getOsSetting('blah', 'group') == 'librenms'

* refactor and remove unneeded load_os/loadOs calls now since getOsSetting automatically loads it.

* restore unix overview graphs, they are different
small cleanups

* fix

LibreNMS/Config.php

@@ -170,7 +170,6 @@ class Config
 
     /**
      * Get a setting from the $config['os'] array using the os of the given device
-     * If that is not set, fallback to the same global config key
      *
      * @param string $os The os name
      * @param string $key period separated config variable name
@@ -180,21 +179,19 @@ class Config
     public static function getOsSetting($os, $key, $default = null)
     {
         if ($os) {
+            \LibreNMS\Util\OS::loadDefinition($os);
+
             if (isset(self::$config['os'][$os][$key])) {
                 return self::$config['os'][$os][$key];
             }
 
-            if (!Str::contains($key, '.')) {
-                return self::get($key, $default);
-            }
-
             $os_key = "os.$os.$key";
             if (self::has($os_key)) {
                 return self::get($os_key);
             }
         }
 
-        return self::get($key, $default);
+        return $default;
     }
 
     /**
@@ -210,7 +207,7 @@ class Config
     public static function getCombined($os, $key, $default = array())
     {
         if (!self::has($key)) {
-            return self::get("os.$os.$key", $default);
+            return self::getOsSetting($os, $key, $default);
         }
 
         if (!isset(self::$config['os'][$os][$key])) {