os/newstore: make collection_list tolerate sloppy start position

os/newstore: make collection_list tolerate sloppy start position

Because of this change (#6076), the hobject_t will contain pool id, hence
the ghobject_t having this hobject_t will be not equal to ghobject_t().

In newstore, this will cause assertion failure:
FAILED assert(k >= start_key && k < end_key)

The fix is to make compatible with previous change to create a
ghobject_t object with pool id and shard id in newstore.

Fixes: #13801
Reported-by: Zhi Zhang <zhangz.david@outlook.com>
Signed-off-by: Sage Weil <sage@redhat.com>