unsupported role: "Instance" errors with EC2 join method

[nklaassen]

Expected behavior:
Nodes can use the EC2 join method with no error logs.

Current behavior:
The following is logged once per minute:

2022-06-21T01:34:42Z INFO [PROC:1]    Joining the cluster with a secure token. pid:10387.1 service/connect.go:576
2022-06-21T01:34:42Z INFO [AUTH]      Attempting registration via proxy server. auth/register.go:177
2022-06-21T01:34:42Z INFO [AUTH]      Attempting registration with auth server. auth/register.go:177
2022-06-21T01:34:42Z WARN [AUTH]      Joining cluster without validating the identity of the Auth Server. This may open you up to a Man-In-The-Middle (MITM) attack if an attacker can gain privileged network access. To remedy this, use the CA pin value provided when join token was generated to validate the identity of the Auth Server. auth/register.go:333
2022-06-21T01:34:42Z ERRO [PROC:1]    Instance failed to establish connection to cluster: unsupported role: "Instance", Post "https://teleport.cluster.local/v2/tokens/register": remote error: tls: internal error. pid:10387.1 service/connect.go:106

Bug details:

• Teleport version
  version 10
• Recreation steps
  join a node/app/db/kube to the cluster using the EC2 join method https://goteleport.com/docs/setup/guides/joining-nodes-aws-ec2/
• Debug logs
  above

@fspmarshall I'm not sure what the "Instance" role does or if this currently breaks anything, but we'll need to fix this, the logs are not nice and it's failing to get certs for the "Instance" role. The EC2 join method does a uniqueness check here and does not know how to check if an "Instance" is unique.