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>