CBQE-0: Changing the default batch size for async load to 1000

Change-Id: I52b719315bdd9104e20e4bdcdf92f35e09010a7f
Reviewed-on: http://review.couchbase.org/40255
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>