osd: always cleanup the scrub results

osd: always cleanup the scrub results

the destructor of Scrub::Store asserts that `this->results` should
always be empty when it is free'd. before this change, if we are
repairing, the results is not flushed or cleaned up, this crashes
osd daemon when a new PG internval comes. also we should not keep
the results around even we don't want to populate them to the omap
if we are repairing, it's just a waste.

Signed-off-by: Kefu Chai <kchai@redhat.com>