Ensure connect callback is invoked on premature socket hangup

Closes brianc#534

Author: Sandro Santilli

Diff for: lib/client.js

@@ -170,9 +170,17 @@ Client.prototype.connect = function(callback) {
       return self.emit('error', error);
     }
     callback(error);
+    callback = null;
   });
 
   con.once('end', function() {
+    if ( callback ) {
+      // haven't received a connection message yet !
+      var err = new Error("Stream unexpectedly ended before getting ready for query execution");
+      callback(err);
+      callback = null;
+      return;
+    }
     if(self.activeQuery) {
       var disconnectError = new Error('Stream unexpectedly ended during query execution');
       self.activeQuery.handleError(disconnectError);