Fixes issue where high id would take a leap after crash

Problem was that the id generator was openened with the highest seen id
passed in as the highId argument when constructing the id generator. It
should have been 0 since at that point whatever is persisted takes
presedence.

Also fixed an issue with silent upgrades of neostore, where those are done
inside a "recovery" block. That problem somehow surfaced after the above
change.