Merge branch '3.4' into 4.1

* 3.4:
  Think positive
  KernelInterface can return null container
  [DI] Detect circular references with ChildDefinition parent
  [VarDumper] Fix global dump function return value for PHP7
  [Ldap] Use shut up operator on connection errors at ldap_start_tls
  Implement startTest rather than startTestSuite
  [OptionsResolver] remove dead code and useless else
  [HttpFoundation] don't override StreamedResponse::setNotModified()
  Added relevent links for parsing to the phpdoc
  Add stricter checking for valid date time string
  Fix symfony/console (optional) dependency for MonologBridge
  [Form] Fix DateTimeType html5 input format

Author: nicolas-grekas

Lock.php

@@ -69,10 +69,10 @@ public function __destruct()
     public function acquire($blocking = false)
     {
         try {
-            if (!$blocking) {
-                $this->store->save($this->key);
-            } else {
+            if ($blocking) {
                 $this->store->waitAndSave($this->key);
+            } else {
+                $this->store->save($this->key);
             }
 
             $this->dirty = true;