Add new shard modes as a map entry to automatically parse them in
`set-mode` command. The change also automatically adds new modes to help
message.
Signed-off-by: Leonard Lyubich <ctulhurider@gmail.com>
`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>
