child_process: fix stdio sockets creation

`readable` and `writable` properties can be passed directly to the
`net.Socket` constructor. This change also avoids an unnecessary call
to `read(0)` on the `stdin` socket. This behavior was disclosed when
trying to merge `[email protected]` and specifically this commit:
libuv/libuv@fd04939.

PR-URL: #18701
Refs: libuv/libuv#1655
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

lib/internal/child_process.js

@@ -227,17 +227,7 @@ function flushStdio(subprocess) {
 
 
 function createSocket(pipe, readable) {
-  var s = new net.Socket({ handle: pipe });
-
-  if (readable) {
-    s.writable = false;
-    s.readable = true;
-  } else {
-    s.writable = true;
-    s.readable = false;
-  }
-
-  return s;
+  return net.Socket({ handle: pipe, readable, writable: !readable });
 }
 
 

test/async-hooks/test-pipewrap.js

@@ -78,7 +78,7 @@ function onexit() {
   // Usually it is just one event, but it can be more.
   assert.ok(ioEvents >= 3, `at least 3 stdout io events, got ${ioEvents}`);
 
-  checkInvocations(pipe1, { init: 1, before: 2, after: 2 },
+  checkInvocations(pipe1, { init: 1, before: 1, after: 1 },
                    'pipe wrap when sleep.spawn was called');
   checkInvocations(pipe2, { init: 1, before: ioEvents, after: ioEvents },
                    'pipe wrap when sleep.spawn was called');