fix: retry idempotent with original body

Fixes: nodejs/node#35925

lib/core/client.js

@@ -1081,8 +1081,6 @@ function write (client, request) {
     if (!expectsPayload) {
       client[kReset] = true
     }
-
-    request.body = null
   } else {
     client[kWriting] = true
 

test/client-idempotent-body.js

@@ -0,0 +1,43 @@
+'use strict'
+
+const { test } = require('tap')
+const { Client } = require('..')
+const { createServer } = require('http')
+
+test('idempotent retry', (t) => {
+  t.plan(11)
+
+  const body = 'world'
+  const server = createServer((req, res) => {
+    let buf = ''
+    req.on('data', data => {
+      buf += data
+    }).on('end', () => {
+      t.strictDeepEqual(buf, body)
+      res.end()
+    })
+  })
+  t.tearDown(server.close.bind(server))
+
+  server.listen(0, () => {
+    const client = new Client(`http://localhost:${server.address().port}`, {
+      pipelining: 2
+    })
+    t.tearDown(client.close.bind(client))
+
+    const _err = new Error()
+
+    for (let n = 0; n < 4; ++n) {
+      client.stream({
+        path: '/',
+        method: 'PUT',
+        idempotent: true,
+        body
+      }, () => {
+        throw _err
+      }, (err) => {
+        t.strictEqual(err, _err)
+      })
+    }
+  })
+})