Improve error message on node joining a cluster with existing state

[klizhentas]

Description

What happened:

• Node has been joined to existing cluster.
• User has tried to join a node to a different cluster.

Node has failed and reported an unclear error

User Message: Get "https://teleport.cluster.local/v2/domain": x509: certificate is valid for *.teleport-staging.example.com, teleport-staging.example.com, not abc1234fgwaetfaegfa.teleport.cluster.local] service/connect.go:867

DEBU [PROC:1]    Failed to connect to Auth Server through tunnel. error:[Get "https://teleport.cluster.local/v2/domain": ssh: handshake
failed: ssh: no authorities for hostname: example.com:443] proxy-addr:example.com:443 service/connect.go:868

ERRO [PROC:1]    Node failed to establish connection to cluster: Failed to connect to Auth Server directly or over tunnel, no methods remaining.. service/connect.go:68

Instead, a node should report more clear error:

This node is already a member of a cluster `cluster-name`. To re-join the node, remove `/var/lib/teleport` and try again.

Server Details

• Teleport version (run teleport version):
• Server OS (e.g. from /etc/os-release):
• Where are you running Teleport? (e.g. AWS, GCP, Dedicated Hardware):
• Additional details:

Client Details

• Tsh version (tsh version):
• Computer OS (e.g. Linux, macOS, Windows):
• Browser version (for UI-related issues):
• Installed via (e.g. apt, yum, brew, website download):
• Additional details:

Debug Logs

Please include or attach debug logs, when appropriate. Obfuscate sensitive information!

• Start Teleport with --debug flag (teleport --debug)
• Run tsh with --debug flag (tsh --debug)

[webvictim]

This is pretty much a duplicate of our favourite #2838