cql3: values: Add unset value to raw_value_view::make_temporary
cql3: values: Add unset value to raw_value_view::make_temporary

When unset_value is passed to make_temporary it gets converted to null_value.
This looks like a mistake, it should be just unset_value.

Signed-off-by: Jan Ciolek <b66a6f3989e26cb552db14b7ab163c3a50292e24@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla