Ensure all streams are explicitly closed

As example:
https://github.com/apache/zeppelin/blob/master/zeppelin-zengine/src/main/java/org/apache/zeppelin/helium/HeliumBundleFactory.java#L220
(no gcis.close() statement)
In order to prevent out-of-memory exceptions or other side effects, I'll work on this improvement of ensuring all (or most) streams life cycle is handled.