Fixes#20335
The major change between Raft v1.6 -> v1.7 was the introduction of the
Prevote feature. Before Prevote, when a partitioned node rejoins a
cluster it may cause an election even if the cluster was stable. Prevote
can avoid this useless election so reintroducing partitioned servers to
an otherwise stable cluster becomes seamless.
Full details: https://github.com/hashicorp/raft/pull/530
In #20335 we discussed whether or not to add a configuration option to
disable prevote in case bugs were discovered. While bugs have been found
(hence the v1.7.1 version as opposed to v1.7.0), I'm choosing to follow
Vault's lead of straightfordwardly bumping the raft dependency:
hashicorp/vault#27605 and hashicorp/vault#28218
