Elasticsearch connector delete and update operations

Hi,

when using the mongo-connector for elasticsearch we discovered two problems.

1. If you specify a index name via `-g DEST_NS_SET` param the generated elasticsearch url which is used for delete operations is wrong. instead of the specified index name it contains the mongo ns value. to fix this we had to add `entry['ns'] = ns` for the oplog_manager.py remove code like its already the case in the update code

2. If you replace an existing document entirely using an update operation (e.g. `db.col.update({"_id" : ObjectId("abc")}, {"a" : 1, "b" : 2 } )` the old document is send to elasticsearch instead of the updated one