Misplaced ratio equals to misplaced_objects deviding misplaced_total, not misplaced_objects / num_objects.
So add a separate metric to show misplaced ratio.
Signed-off-by: haoyixing <haoyixing@kuaishou.com>
- `ceph.Conn` interface no longer depends on go-ceph/rados,
now defines its own `PoolStat` structure for our use.
- New separate `rados` package that implements the interface
- Merged `mocks` package into `ceph` to avoid circular import