Fix vfs not always connecting if first node binary in list doesn't exist

We'd first get a EPIPE and then an ENOENT in this scenario,
breaking our retry behavior.

node_modules/vfs-child/parent.js

@@ -1,6 +1,7 @@
 var Consumer = require('vfs-socket/consumer').Consumer;
 var inherits = require('util').inherits;
 var spawn = require('child_process').spawn;
+var fs = require("fs");
 
 exports.Parent = Parent;
 
@@ -23,27 +24,39 @@ function Parent(fsOptions) {
     // Override Consumer's connect since the transport logic is internal to this module
     this.connect = connect.bind(this);
     function connect(callback) {
+        var _self = this;
         try {
+            // Check if file exists first; spawn's ENOENT may arrive after other errors
+            if (!fs.existsSync(nodeBin[0]))
+                return tryNext(new Error("Couldn't find valid node binary"));
             child = spawn(nodeBin[0], args, options).on("error", tryNext);
         }
         catch (e) {
-            return tryNext(e);
+            return done(e);
         }
         child.stdin.readable = true;
-        Consumer.prototype.connect.call(this, [child.stdout, child.stdin], tryNext);
+        Consumer.prototype.connect.call(this, [child.stdout, child.stdin], done);
         child.on("exit", disconnect);
         child.stdin.resume();
-        var _self = this;
-        // try all possible locations of node before giving up
-        function tryNext(err, vfs) {
-            if (!child) return;
-            child.removeListener("error", tryNext);
-            child.on("error", function ignore() {});
-            if (err && err.code == "ENOENT" && nodeBin.length > 1) {
-                child = null;
+        
+        function tryNext(err) {
+             if (nodeBin.length > 1) {
                 nodeBin.shift();
                 _self.emit("error", err);
                 _self.connect(callback);
+             } else {
+                 return done(err);
+             }
+        }
+        
+        function done(err, vfs) {
+            if (!child) return;
+            child.removeListener("error", done);
+            child.on("error", function ignore(err) {});
+            child = null;
+            
+            if (err && err.code == "ENOENT") {
+                tryNext(err);
             } else {
                 callback(err, vfs);
             }