CBQE-1246: handle EOFError in BatchedLoadDocumentsTask

Change-Id: I2ee4e91bd3dc3731bc06d70e12d47b56bde5ac85
Reviewed-on: http://review.couchbase.org/25869
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>