[Release 1.26] Support server flag for tailscale

[manuelbuil]

Backport: #7824

[est-suse]

##Environment Details

COMMIT=e200425876a1da9c636a62e8c8748206f50a9488
k3s version v1.26.6+k3s-e2004258 (e2004258)
go version go1.19.10

Infrastructure

Cloud
Node(s) CPU architecture, OS, and version:

Linux 5.14.21-150400.24.11-default x86_64 GNU/Linux 
PRETTY_NAME="SUSE Linux Enterprise Server 15 SP4"

Cluster Config

ip-1-2-1-1   Ready    control-plane,etcd,master   62s    v1.26.6+k3s-e2004258
ip-1-1-1-2   Ready    control-plane,etcd,master   4m6s   v1.26.6+k3s-e2004258

Config.yaml

write-kubeconfig-mode: 644
debug: true
token: caseofthemondaysfrozenvegetables
protect-kernel-defaults: true
cluster-init: true
vpn-auth: "name=tailscale,joinKey=cWildTurkeysRunGooseLoose,controlServerURL=http://headscale.sceniccarcinogenicclouds.tech"

Pretty Simple Validation

$ curl -fsSL https://tailscale.com/install.sh | sh
$ sudo INSTALL_K3S_COMMIT=2eddfe6cf4e67b7d6aab0fe8311d72372030459e INSTALL_K3S_EXEC=server ./install-k3s.sh 
$ ip a | grep tailscale
$ kgn //kubectl get nodes
$ kgp -A //kubectl get pods -A
$ get_report //generate this template

ip a | grep tailscale

ip a | grep tailscale
19: tailscale0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1280 qdisc pfifo_fast state UNKNOWN group default qlen 500
    inet 100.64.0.3/32 scope global tailscale0

kgp -A

NAMESPACE     NAME                                      READY   STATUS      RESTARTS   AGE
kube-system   coredns-59b4f5bbd5-vkp2f                  1/1     Running     0          6m9s
kube-system   helm-install-traefik-crd-w7x88            0/1     Completed   0          6m9s
kube-system   helm-install-traefik-q5g74                0/1     Completed   1          6m9s
kube-system   local-path-provisioner-76d776f6f9-n8scn   1/1     Running     0          6m9s
kube-system   metrics-server-68cf49699b-95gmc           1/1     Running     0          6m9s
kube-system   svclb-traefik-4266c48e-bp26w              2/2     Running     0          5m34s
kube-system   svclb-traefik-4266c48e-j2hft              2/2     Running     0          3m20s
kube-system   traefik-57c84cf78d-fm9vj                  1/1     Running     0          5m34s