Fix xml-attribute-map for the xml driver

[romantomchak]

There is a simple test XML reference for class Foo:

<?xml version="1.0" encoding="UTF-8"?>
<serializer>
    <class name="Foo">
        <property name="array" type="array" xml-attribute-map="true" />
    </class>
</serializer>

class Foo
{
    private $array = [
        'name' => 'firstname',
        'value' => 'lastname'
    ];
}

When I try serialize this class I'm expecting to get the result as shown below but instead getting an error that the property array cannot be serialized because it contains not allowed characters.

<result name="firstname" value="lastname"/>

After investigation I found the mismatch between xml file property and property in metadata class.
This commit fixed this issue.

[goetas]

👍

[goetas]

Thank you