Merge pull request #335 from solariumphp/revert-334-fix-curl

Revert "Fix curl headers for solr > 5"

library/Solarium/Core/Client/Adapter/Curl.php

@@ -156,11 +156,7 @@ class Curl extends Configurable implements AdapterInterface
         }
 
         if (!isset($options['headers']['Content-Type'])) {
-            if($method == Request::METHOD_GET){
-                $options['headers']['Content-Type'] = 'application/x-www-form-urlencoded; charset=utf-8';
-            } else {
-                $options['headers']['Content-Type'] = 'application/xml; charset=utf-8';
-            }
+            $options['headers']['Content-Type'] = 'text/xml; charset=utf-8';
         }
 
         // Try endpoint authentication first, fallback to request for backwards compatibility