Merge branch '2.8' into 3.0

* 2.8:
  [Finder] Partially revert #17134 to fix a regression
  [HttpKernel] Fix mem usage when stripping the prod container
  exception when registering bags for started sessions

Conflicts:
	src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
	src/Symfony/Component/Validator/composer.json

Author: nicolas-grekas

Iterator/FilterIterator.php

@@ -39,11 +39,18 @@ public function rewind()
         while ($iterator instanceof \OuterIterator) {
             $innerIterator = $iterator->getInnerIterator();
 
-            if ($innerIterator instanceof \FilesystemIterator) {
+            if ($innerIterator instanceof RecursiveDirectoryIterator) {
+                // this condition is necessary for iterators to work properly with non-local filesystems like ftp
+                if ($innerIterator->isRewindable()) {
+                    $innerIterator->next();
+                    $innerIterator->rewind();
+                }
+            } elseif ($innerIterator instanceof \FilesystemIterator) {
                 $innerIterator->next();
                 $innerIterator->rewind();
             }
-            $iterator = $iterator->getInnerIterator();
+
+            $iterator = $innerIterator;
         }
 
         parent::rewind();