drill

d7eebec4 - DRILL-2274: Unable to allocate sv2 buffer after repeated attempts : JOIN, Order by used in query

DRILL-2274: Unable to allocate sv2 buffer after repeated attempts : JOIN, Order by used in query - when ExternalSortBatch.newSV2() couldn't allocate a new SV2 it spills the spilledBatchGroups instead of batchGroups, otherwise no memory will be released for the sort's allocator - copierAllocator is closed as soon as possible to free more memory for the sort this closes #172