minor #19617 Use try-finally where it possible (Koc)

This PR was merged into the 3.1 branch.

Discussion
----------

Use try-finally where it possible

| Q             | A
| ------------- | ---
| Branch?       | 3.1
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Just a minior refactoring for using PHP 5.5 feature.

Commits
-------

747ddf6 Use try-finally where it possible

Author: fabpot

Compiler/AutowirePass.php

@@ -45,21 +45,15 @@ public function process(ContainerBuilder $container)
                     $this->completeDefinition($id, $definition);
                 }
             }
-        } catch (\Exception $e) {
-        } catch (\Throwable $e) {
-        }
-
-        spl_autoload_unregister($throwingAutoloader);
-
-        // Free memory and remove circular reference to container
-        $this->container = null;
-        $this->reflectionClasses = array();
-        $this->definedTypes = array();
-        $this->types = null;
-        $this->ambiguousServiceTypes = array();
-
-        if (isset($e)) {
-            throw $e;
+        } finally {
+            spl_autoload_unregister($throwingAutoloader);
+
+            // Free memory and remove circular reference to container
+            $this->container = null;
+            $this->reflectionClasses = array();
+            $this->definedTypes = array();
+            $this->types = null;
+            $this->ambiguousServiceTypes = array();
         }
     }