Pass cacheMetadata option through to collection.

Without this the metadata cache will *always* use `_cake_model_` which
is not how the code should work.

src/Database/Schema/Collection.php

@@ -60,7 +60,7 @@ public function __construct(Connection $connection) {
 		$config = $this->_connection->config();
 
 		if (!empty($config['cacheMetadata'])) {
-			$this->cacheMetadata(true);
+			$this->cacheMetadata($config['cacheMetadata']);
 		}
 	}