Don't skip relationships in the cache on rollback.

When loading relationships for a node, and the relationship chain
has been partially loaded, it was possible for another transaction
to make modifications to the next relationship to be loaded for
that node, but without loading it through that node (by loading it
through the other node of that relationship). If that transaction
rolled back it would make the cache skip loading that relationship.
Merge pull request #2769 from thobe/1.9-partial-relchain-load

Don't skip relationships in the cache on rollback.