ovsdb-tool: Add a db consistency check to the ovsdb-tool check-cluster command.

ovsdb-tool: Add a db consistency check to the ovsdb-tool check-cluster command.

There are some occurrences where the database ends up in an inconsistent
state. This happened in ovn-k8s and is described in [0].
Here we are adding a supported way to check that a given db is consistent,
which is less error prone than checking the logs.

Tested against both a valid db and a corrupted db attached to the
above bug [1]. Also, tested  with a fresh db that did not do a snapshot.

[0]: https://bugzilla.redhat.com/show_bug.cgi?id=1837953#c23
[1]: https://bugzilla.redhat.com/attachment.cgi?id=1697595

Signed-off-by: Federico Paolinelli <fpaoline@redhat.com>
Suggested-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>