Fix custom blueprints

[mansona]

This fixes the use of ember-cli-update with the v2 addon blueprint https://github.com/embroider-build/addon-blueprint

I know there are a few tests to fix but it shows the main things that needed to change:

• use latest ember-cli for custom blueprints because it was locking down to 3.16 before because of the lastNode8Version
• remove -sb which I'm assuming was --skip-bower

I'm going to get tests passing on this but I'm wondering if now is a good time to remove the lastNode8Version since it has the comment // remove when node 8 is dropped which has already happened 🤔

[kellyselden]

LGTM. I don't know what's up with CI.