Fix global merge on 1node regression
Fix global merge on 1node regression

On a 1node system, global merge was failing, because the key array was not
being cleared properly

Signed-off-by: Jake Smith <b20121000db38205734e8ca1c74fe9668b08552a@lexisnexis.com>

afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform