Add a common error for this case because it is not an error
which should increase error counter. Single error simplifies checks on
the call-site.
Signed-off-by: Evgenii Stratonikov <evgeniy@morphbits.ru>
This check should occur on the shard level, but because
blobstor components expose `Open(readOnly bool)` interface,
it is reasonable to expect an error here.
Signed-off-by: Evgenii Stratonikov <evgeniy@morphbits.ru>
