keyring: fix flake in replication-after-election test (#13749)
keyring: fix flake in replication-after-election test (#13749)

The test for simulating a key rotation across leader elections was
flaky because we weren't waiting for a leader election and was
checking the server configs rather than raft for which server was
currently the leader. Fixing the flake revealed a bug in the test that
we weren't ensuring the new leader was running its own replication, so
it wouldn't pick up the key material from the previous follower.
hashicorp/nomad,hashicorp/nomad,hashicorp/nomad,hashicorp/nomad,hashicorp/nomad,hashicorp/nomad