Fix kubelet.conf server line indentation (#13284)

The lineinfile tasks that rewrite the server field in kubelet.conf
replaced the whole line with a hard-coded indentation, corrupting the
file when the existing entry was indented differently. Capture the
original leading whitespace with a group regexp and restore it via
backrefs so the rewrite preserves the surrounding YAML structure.

Signed-off-by: longyuxiang <longyuxiang@kylinos.cn>

roles/kubernetes/kubeadm/tasks/main.yml

@@ -103,8 +103,9 @@
 - name: Update server field in kubelet kubeconfig
   lineinfile:
     dest: "{{ kube_config_dir }}/kubelet.conf"
-    regexp: 'server:'
-    line: '    server: {{ kube_apiserver_endpoint }}'
+    regexp: '^(\s+)server: https.*'
+    line: '\1server: {{ kube_apiserver_endpoint }}'
+    backrefs: true
     backup: true
   when:
     - kubeadm_config_api_fqdn is not defined
@@ -115,8 +116,9 @@
 - name: Update server field in kubelet kubeconfig - external lb
   lineinfile:
     dest: "{{ kube_config_dir }}/kubelet.conf"
-    regexp: '^    server: https'
-    line: '    server: {{ kube_apiserver_endpoint }}'
+    regexp: '^(\s+)server: https.*'
+    line: '\1server: {{ kube_apiserver_endpoint }}'
+    backrefs: true
     backup: true
   when:
     - ('kube_control_plane' not in group_names)