rgw: orphans find: don't process stale bucket instances

rgw: orphans find: don't process stale bucket instances

As a large bucket might have resharded multiple times, check the cur bucket info
and ensure that no reshard is in progress before we attempt to log bucket index
entries. On a large sized bucket, since a bucket would have undergone reshard
multiple times, this avoids wasteful processing of stale bucket instance entries

Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>
(cherry picked from commit 5436ff7fa99061a489f089677c03f63c76bb954b)

 Conflicts:
	src/rgw/rgw_orphan.cc
sys_objctx dropped as obj_ctx changes are a part of Nautilus. Also similarly
	with the includes, only `rgw_bucket.h` is included