os/bluestore: prefix omap of temp objects by real pool

os/bluestore: prefix omap of temp objects by real pool

For recovery or backfill, we use temp object at destination
if the whole object context can not sent in one shot.
And since https://github.com/ceph/ceph/pull/29292, we now segregate
omap keys by object's binding pool.
However, https://github.com/ceph/ceph/pull/29292 does not
work well for recovery or backfill process that need
to manipulate temp objects because we always (deliberately)
assign a negative pool id for each temp object which is
(obviously) different from the corresponding target object,
and we do not fix it when trying to rename the temp object
back to the target object at the end of recovery/backfill,
as a result of which we totally lose track of the omap
portion of the recovered object.

Fix by prefixing all omap-related stuff of temp objects
by using its real(pg's) pool.

Signed-off-by: xie xingguo <xie.xingguo@zte.com.cn>