Raft: assorted cleanups (golint and go vet)

Mostly comments and non-functional changes, with a few bug fixes for format strings in tests.
I find the tags misleading because it looks like a map, and if it were a map the order wouldn't matter as long as the keys and values match up. The labels here are not used by the compiler so they can only serve to confuse a human. I could also change these from arrays to maps to keep the labels and remove the order-dependence.