Only returns status of a port after connection closed.

Originally, if trying to immediately connect to a port returned from the status
check, the socket connection may not have finished closing. Now returns the
status after the connection has finished closing on the socket.

lib/portscanner.js

@@ -54,25 +54,31 @@ portscanner.findAPortNotInUse = function(startPort, endPort, host, callback) {
 portscanner.checkPortStatus = function(port, host, callback) {
   host = host || 'localhost'
   var socket = new Socket()
+    , status = null
 
   // Socket connection established, port is open
   socket.on('connect', function() {
+    status = 'open'
     socket.end()
-    callback(null, 'open')
   })
 
   // If no response, assume port is not listening
   socket.setTimeout(400)
   socket.on('timeout', function() {
+    status = 'closed'
     socket.end()
-    callback(null, 'closed')
   })
 
   // Assuming the port is not open if an error. May need to refine based on
   // exception
   socket.on('error', function(exception) {
+    status = 'closed'
     socket.destroy()
-    callback(null, 'closed')
+  })
+
+  // Return after the socket has closed
+  socket.on('close', function(exception) {
+    callback(null, status)
   })
 
   socket.connect(port, host)