[DBUtil] correct column def comparison. fixes #1121 refs #975

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | na
| Fixed tickets | #1121
| Refs tickets  | #975, #1121, https://github.com/zikula-modules/News/issues/123
| License       | MIT
| Doc PR        | na

ping @rgasch