osd/../_client_request: skip recover_missing_snaps if none are missing

osd/../_client_request: skip recover_missing_snaps if none are missing

For every clone object operation, we call recover_missing_snaps
to make sure that the resolved object is not missing.
For us to resolve_oid we need to lock the obc for RWREAD.
See ClientRequest::recover_missing_snaps.

Let's avoid locking the object if I don't have any possible
missing clone objects. Otherwise, try to recover as before.

This should positively affect reads even in an undegraded cluster state.

Signed-off-by: Matan Breizman <mbreizma@redhat.com>