Stop ScanAndScrollTest from failing spuriously

ScanAndScrollTest->testQuerySizeOverride used the rewind method on
ScanAndScroll which executes a scroll query on Elasticsearch without making
sure that the index is fully allocated.  Apparently, this can cause
Elasticsearch to throw back an error.  We work around this by adding a
refresh before the rewind.
Merge pull request #635 from nik9000/fix_test3

Stop ScanAndScrollTest from failing spuriously