Do not try clearing locked files in cache folder

lib/private/cache/file.php

@@ -177,10 +177,17 @@ class File implements ICache {
 			}
 			while (($file = readdir($dh)) !== false) {
 				if ($file != '.' and $file != '..') {
+					try {
 						$mtime = $storage->filemtime('/' . $file);
 						if ($mtime < $now) {
 							$storage->unlink('/' . $file);
 						}
+					} catch (\OCP\Lock\LockedException $e) {
+						// ignore locked chunks
+						\OC::$server->getLogger()->debug('Could not cleanup locked chunk "' . $file . '"', array('app' => 'core'));
+					} catch (\OCP\Files\LockNotAcquiredException $e) {
+						\OC::$server->getLogger()->debug('Could not cleanup locked chunk "' . $file . '"', array('app' => 'core'));
+					}
 				}
 			}
 		}