ignition: start kubeadm after network.target

In certain baremetal environments, where there are multiple connected
and/or disconnected network ports, the network target is reached more
slowly, and the kubeadm.service might fail because it does not have the
proper pre-kubeadm commands correctly done (like a ctr image pull) or it
cannot connect to other k8s nodes.

bootstrap/kubeadm/internal/ignition/clc/clc.go

@@ -96,6 +96,7 @@ systemd:
         Description=kubeadm
         # Run only once. After successful run, this file is moved to /tmp/.
         ConditionPathExists=/etc/kubeadm.yml
+        After=network.target
         [Service]
         # To not restart the unit when it exits, as it is expected.
         Type=oneshot

bootstrap/kubeadm/internal/ignition/clc/clc_test.go

@@ -249,7 +249,7 @@ func TestRender(t *testing.T) {
 				Systemd: types.Systemd{
 					Units: []types.Unit{
 						{
-							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
+							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\nAfter=network.target\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
 							Enabled:  pointer.Bool(true),
 							Name:     "kubeadm.service",
 						},
@@ -340,7 +340,7 @@ func TestRender(t *testing.T) {
 				Systemd: types.Systemd{
 					Units: []types.Unit{
 						{
-							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
+							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\nAfter=network.target\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
 							Enabled:  pointer.Bool(true),
 							Name:     "kubeadm.service",
 						},
@@ -423,7 +423,7 @@ func TestRender(t *testing.T) {
 				Systemd: types.Systemd{
 					Units: []types.Unit{
 						{
-							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
+							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\nAfter=network.target\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
 							Enabled:  pointer.Bool(true),
 							Name:     "kubeadm.service",
 						},
@@ -550,7 +550,7 @@ func TestRender(t *testing.T) {
 				Systemd: types.Systemd{
 					Units: []types.Unit{
 						{
-							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
+							Contents: "[Unit]\nDescription=kubeadm\n# Run only once. After successful run, this file is moved to /tmp/.\nConditionPathExists=/etc/kubeadm.yml\nAfter=network.target\n[Service]\n# To not restart the unit when it exits, as it is expected.\nType=oneshot\nExecStart=/etc/kubeadm.sh\n[Install]\nWantedBy=multi-user.target\n",
 							Enabled:  pointer.Bool(true),
 							Name:     "kubeadm.service",
 						},