ovsdb: transaction: Fix logging order of duplicate index rows.

ovsdb: transaction: Fix logging order of duplicate index rows.

The message about conflicting rows is trying to order the two rows
in a consistent manner, so the log messages do not change in tests.
But it fails to do so, because the order of columns in the column
set depends on the order of columns inside the hash map, which
depends on the hash function and the internal implementation details
of the hash map.  This results in random test failures, when two
rows end up in the opposite order.

Uncovered while testing a different hash map implementation, but the
failure is technically possible even without any changes in the code,
e.g., by running on a different CPU architecture or with different
compiler flags.

Fix that by introducing a new function that constructs the column
set with columns in a predictable order and without UUID columns that
have random values in most cases and so not actually comparable.

Fixes: 6910a6e6f25f ("ovsdb: Implement table uniqueness constraints ("indexes").")
Reported-by: Rosemarie O'Riorden <rosemarie@redhat.com>
Acked-by: Eelco Chaudron echaudro@redhat.com
Acked-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>