FD3-790 bugfix in kea config. client classes must be unique

src/KeaBundle/Services/BaseKea.php

@@ -104,6 +104,7 @@ class BaseKea implements KeaConfigInterface
      */
     private function subnetConfig($subnets, $reservations)
     {
+        $classes = [];
         foreach ($subnets as $subnet) {
             $pools = [];
             foreach ($subnet->getIpPool() as $pool) {
@@ -146,9 +147,12 @@ class BaseKea implements KeaConfigInterface
 
             if ($client_class != '') {
                 $subnetConf['client-class'] = $client_class;
-                $this->client_classes [] = [
-                    'name' => $client_class,
-                ];
+                if (!in_array($client_class, $classes)) {
+                    $classes[] = $client_class;
+                    $this->client_classes[] = [
+                        'name' => $client_class,
+                    ];
+                }
             }
 
             $netgroup = $subnet->getNetGroup();