Remove freshness checks, always insert documents

It's basically more overhead for a minimally used case and
makes the code more complex.

Change-Id: Ib11506563be08745d8b88e122134e574e600ff64
Tighten up returns in LinksUpdateJob

We only want to return false when we *know* we failed. On null
conditions we want to just keep going like before.

Change-Id: I5753bf81401e838f5cb278f4d1774145267b1495
LinksUpdateSecondary: Avoid pointless extra iteration and return clearly

Change-Id: Ibcb0c4a4aeb87d5ea19113a66c132ed4005a39fc
Merge "Remove freshness checks, always insert documents"
Merge "Tighten up returns in LinksUpdateJob"
Merge "LinksUpdateSecondary: Avoid pointless extra iteration and return clearly"