Currently, when removing shard special care must be taken with respect
to shard numbering. `mode: disabled` allows to leave shard configuration
in place while also ignoring it during initialization. This makes
disk replacement much more convenient.
Signed-off-by: Evgenii Stratonikov <evgeniy@morphbits.ru>
`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>
