[Release 1.25] Fix a couple of tailscale integration issues

[manuelbuil]

Backports: #7771 #7772

[ShylajaDevadiga]

Validated on k3s version v1.25.11-rc1+k3s1 (a0954e5), logs show useful message when auth key is expired or invalid

Environment Details

Infrastructure
Cloud EC2 instance

Node(s) CPU architecture, OS, and Version:
SLES 15 SP3

Cluster Configuration:
Single node

Config.yaml:

write-kubeconfig-mode: 644
token: secret
cluster-init: true
vpn-auth: "name=tailscale,joinKey=tskey-auth-PASSKEY"

Steps to reproduce the issue and validate the fix

1. Copy config.yaml
2. Install tailscale
3. Install k3s passing the invalid authkey
4. Check logs

Before fix:

Jun 16 07:46:31 ip-172-31-6-131 k3s[18018]: time="2023-06-16T07:46:31Z" level=info msg="Starting VPN: tailscale"
Jun 16 07:46:32 ip-172-31-6-131 k3s[18018]: exit status 1

After fix:

un 16 07:46:28 ip-172-31-5-25 k3s[17766]: time="2023-06-16T07:46:28Z" level=info msg="Starting VPN: tailscale"
Jun 16 07:46:28 ip-172-31-5-25 k3s[17766]: time="2023-06-16T07:46:28Z" level=fatal msg="tailscale up failed: backend error: invalid key: API key kE7PfU6CNTRL not valid\n: exit status 1"

[ShylajaDevadiga]

Related issue: #7772