cmd/k8s-operator/deploy/manifests: check if IPv6 module is loaded before using it (#11867)

Before attempting to enable IPv6 forwarding in the proxy init container
check if the relevant module is found, else the container crashes
on hosts that don't have it.

Updates#11860

Signed-off-by: Irbe Krumina <irbe@tailscale.com>

cmd/k8s-operator/deploy/manifests/proxy.yaml

@@ -14,10 +14,8 @@ spec:
         - name: sysctler
           securityContext:
             privileged: true
-          command: ["/bin/sh"]
-          args:
-            - -c
-            - sysctl -w net.ipv4.ip_forward=1 net.ipv6.conf.all.forwarding=1
+          command: ["/bin/sh", "-c"]
+          args: [sysctl -w net.ipv4.ip_forward=1 && if sysctl net.ipv6.conf.all.forwarding; then sysctl -w net.ipv6.conf.all.forwarding=1; fi]
       resources:
         requests:
           cpu: 1m