Raise ValueError if sort_dir is unknown

Raise ValueError in case of KeyError, when sort_dir is not
'asc' or 'desc'.

ValueError while adding pagination has never been raised before,
because if sort direction was incorrect, KeyError has been
raised while adding sorting.

Change-Id: Ia0366dbdf38557c4e6a9307fb27c77fd1c1873c3
Merge "Raise ValueError if sort_dir is unknown"