Unused variable scanned_tuples in LVRelStats

Hi,

scanned_tuples variable in LVRelStats is introduced by commit b4b6923e
but it seems to me that it's actually not used. We store num_tuples
into vacrelstats->scanned_tuples after scanned all blocks, and the
comment mentioned that saving it in order to use later but we actually
use num_tuples instead of vacrelstats->scanned_tuples from there. I
think the since the name of scanned_tuples implies more clearer
purpose than num_tuples it's better to use it instead of num_tuples,
or we can remove scanned_tuples from LVRelStats.

/* save stats for use later */
vacrelstats->scanned_tuples = num_tuples;
vacrelstats->tuples_deleted = tups_vacuumed;
vacrelstats->new_dead_tuples = nkeep;

Attached small path fixes this.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center