extract clone duplication logic in exceptionlistener

Drupal needs potentially to adapt the exception listener to add more information from the original request. (see http://drupal.org/node/2057607) so what about extracing some of the logic into a new method.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT