Do not check storage availability for getOwner

Because the owner is always known thanks to the file cache and other
places, we don't need the remote storage to be actually available.

lib/private/files/storage/wrapper/availability.php

@@ -399,7 +399,6 @@ class Availability extends Wrapper {
 
 	/** {@inheritdoc} */
 	public function getOwner($path) {
-		$this->checkAvailability();
 		try {
 			return parent::getOwner($path);
 		} catch (\OCP\Files\StorageNotAvailableException $e) {