Use current user to filter validation tasks in publication workflow.

We need to use the current user to filter the validaton tasks in publication workflow.

NXP-8094 is a side effect of this bug.
Indeed, if a user submits a doc to publication, as the validation tasks are not filtered with the current user, the CoreProxyWithWorkflowFactory considers that this user has validation tasks (since a task actually exists, but assigned to Administrator), so the "Publish/Reject" buttons are displayed in the summary tab of the proxy.

See <h:panelGroup rendered="#{publishActions.hasValidationTask()}"> in publication_widget_template.xhtml.