os: don't use getCheckedFunction() in userInfo()

os.userInfo() takes an optional object as its first argument.
getCheckedFunction() adds a context object to the argument list
passed to the binding layer. The context object has the potential
to confuse the binding layer, particularly if an error occurs.
This commit makes userInfo() explicitly call into the binding
layer with two arguments.

lib/os.js

@@ -40,7 +40,7 @@ const {
   getOSType: _getOSType,
   getPriority: _getPriority,
   getTotalMem,
-  getUserInfo: _getUserInfo,
+  getUserInfo,
   getUptime,
   isBigEndian,
   setPriority: _setPriority
@@ -64,7 +64,6 @@ const getHostname = getCheckedFunction(_getHostname);
 const getInterfaceAddresses = getCheckedFunction(_getInterfaceAddresses);
 const getOSRelease = getCheckedFunction(_getOSRelease);
 const getOSType = getCheckedFunction(_getOSType);
-const getUserInfo = getCheckedFunction(_getUserInfo);
 
 getFreeMem[Symbol.toPrimitive] = () => getFreeMem();
 getHostname[Symbol.toPrimitive] = () => getHostname();
@@ -239,6 +238,19 @@ function getPriority(pid) {
   return priority;
 }
 
+function userInfo(options) {
+  if (typeof options !== 'object')
+    options = null;
+
+  const ctx = {};
+  const user = getUserInfo(options, ctx);
+
+  if (user === undefined)
+    throw new ERR_SYSTEM_ERROR(ctx);
+
+  return user;
+}
+
 module.exports = {
   arch,
   cpus,
@@ -255,7 +267,7 @@ module.exports = {
   tmpdir,
   totalmem: getTotalMem,
   type: getOSType,
-  userInfo: getUserInfo,
+  userInfo,
   uptime: getUptime,
 
   // Deprecated APIs