bug symfony#22401 [3.2] Prevent double registrations related to tag priorities (nicolas-grekas)

This PR was merged into the 3.2 branch.

Discussion
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[3.2] Prevent double registrations related to tag priorities

| Q             | A
| ------------- | ---
| Branch?       | 3.2
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

symfony#22396 and symfony#22399 on 3.2

Commits
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ec6a2f9 [3.2] Prevent double registrations related to tag priorities

Author: fabpot

src/Symfony/Component/DependencyInjection/Compiler/PriorityTaggedServiceTrait.php

@@ -40,11 +40,9 @@ private function findAndSortTaggedServices($tagName, ContainerBuilder $container
     {
         $services = array();
 
-        foreach ($container->findTaggedServiceIds($tagName) as $serviceId => $tags) {
-            foreach ($tags as $attributes) {
-                $priority = isset($attributes['priority']) ? $attributes['priority'] : 0;
-                $services[$priority][] = new Reference($serviceId);
-            }
+        foreach ($container->findTaggedServiceIds($tagName) as $serviceId => $attributes) {
+            $priority = isset($attributes[0]['priority']) ? $attributes[0]['priority'] : 0;
+            $services[$priority][] = new Reference($serviceId);
         }
 
         if ($services) {