Add *.test to gitignore.

These files are left by some go commands.
Raft: fix problems reported by golint.
Raft: fix printf strings found by go vet.
raft: remove misleading labels in array definition

Since these are arrays instead of maps, the "keys" here are actually
(useless) goto labels. What really matters is that the ordering is
the same between the constant declarations and the array.
Raft: a few more improvements to test messages.
Merge pull request #1257 from bdarnell/cleanups

Raft: assorted cleanups (golint and go vet)