save username/password in handshake command to use them for auth_switch request response

Author: sidorares

lib/commands/client_handshake.js

@@ -36,12 +36,18 @@ ClientHandshake.prototype.sendCredentials = function (connection) {
     console.log('Sending handshake packet: flags:%d=(%s)', this.clientFlags,
       flagNames(this.clientFlags).join(', '));
   }
+
+  this.user = connection.config.user;
+  this.password = connection.config.password;
+  this.passwordSha1 = connection.config.passwordSha1;
+  this.database = connection.config.database;
+
   var handshakeResponse = new Packets.HandshakeResponse({
     flags   : this.clientFlags,
-    user    : connection.config.user,
-    database: connection.config.database,
-    password: connection.config.password,
-    passwordSha1   : connection.config.passwordSha1,
+    user    : this.user,
+    database: this.database,
+    password: this.password,
+    passwordSha1   : this.passwordSha1,
     charsetNumber  : connection.config.charsetNumber,
     authPluginData1: this.handshake.authPluginData1,
     authPluginData2: this.handshake.authPluginData2,