The problem was that LooseScan execution code assumed that tab->key holds 
the index used for looseScan. This is only true when range or full index
scan are used. In case of ref access, the index is in tab->ref.key (and 
tab->index==0 which explains how LooseScan passed tests with ref access: they 
used one index)

Fixed by setting/using loosescan_key, which always the correct index#.