Can't get index status while index is being closed

[jan-niestadt]

When using BLS (in "AutoSearch mode") to add data to an index, the index status is being polled while the indexing takes place. This works fine in the beginning, but after a while, the status request remains pending for a number of seconds until the indexing process is finished. This is probably because of synchronized methods in Index.java blocking the status request. We can probably improve this by being more specific about what we synchronize on, and/or keeping track of an extra status variable.