need direction on bug with invalidateblock

[BrannonKing]

The invalidateblock command has a bug wherein it doesn't follow side-chains with more work (after the best chain is invalidated).

See lbryio/lbcd#86 .

Is this because the getReorganizeNodes -> bestchain.FindFork doesn't account for the newly invalidated nodes (since they haven't been invalidated at the time it's called)?

Would calling getReorganizeNodes again after the invalidations work?

Any other ideas on how to fix this issue?

[zquestz]

NOTE: This PR probably needs to be ported over.

btcsuite/btcd#2196