`Degraded` mode can be set by the administrator if needed.
Modifying operations in this mode can lead node into an inconsistent state
because metabase checks such as lock checking are not performed.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
If the key can't be fetched, an error is always returned, so it makes
sense to fail the whole command inside of a `key.Get*()`.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
