Use model::class instead of string for binding (#11450)

* Use model::class instead of string for binding

Originally from laravel shift

Shift bindings

PHP 5.5.9+ adds the new static `class` property which provides the fully qualified class name. This is preferred over using class name strings as these references are checked by the parser.

* Shift cleanup

app/Models/MplsLspPath.php

@@ -47,6 +47,6 @@ class MplsLspPath extends Model implements Keyable
 
     public function lsp()
     {
-        return $this->belongsTo('App\Models\MplsLsp', 'lsp_id');
+        return $this->belongsTo(\App\Models\MplsLsp::class, 'lsp_id');
     }
 }