osd: Change default value of osd_pg_delete_cost

osd: Change default value of osd_pg_delete_cost

osd_pg_delete_cost defines the cost of the PG deletion operation.
This cost is used by WPQ to determine which operation should be dequeued. Lower the cost, higher the chance of the operation being dequeued next.
mClock scheduler uses the cost parameter in a similar way.
However, with the osd_delete_sleep_ssd and osd_delete_sleep_hdd options disabled with mClock, we noticed that PG deletion was completing much faster with mClock scheduler.
In order to achieve behavior similar to WPQ with mClock scheduler, the osd_pg_delete_cost has been increased.

Signed-off-by: Aishwarya Mathuria <amathuri@redhat.com>