Fix EZP-21807: link is duplicated on table row insertion

JIRA: https://jira.ez.no/browse/EZP-21807

# Description

This is the same issue as [EZP-20355](https://jira.ez.no/browse/EZP-20355) (see the description of the PR #561) but for links.

# Tests

manual tests in IE (8, 9 and 10), Chrome and Firefox