records: display tabs

(closes #1646)

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
move this function to `invenio.modules.comments.utils` or create new method on `invenio.modules.comments.models: CmtRECORDCOMMENT` (https://github.com/inveniosoftware/invenio/blob/pu/invenio/modules/comments/models.py#L34)