osd: report -EINVAL to on_finish in asok_route_to_pg catch

The handler passed the stale locate result (0) while returning -EINVAL,
so callers saw success on a bad_cmd_get failure.

Only reachable via the "scrubdebug" asok command (the sole user of
asok_route_to_pg) when a parameter fails type parsing.

Signed-off-by: Sun Yuechi <sunyuechi@iscas.ac.cn>