MODE-2123 Changed the code so that new nodes never try to find themselves in the workspace cache

Also fixed some resulting regressions for specific situations. See @hchiorean's [original PR](https://github.com/ModeShape/modeshape/pull/1019) for some discussion about these regressions.

This should be merged into the 'master' branch and cherry-picked into the '3.6.x' branch.