title: <SpringProperty> is always undefined and default value does not work
body: <p>I have springproperty:</p>
  <pre><code>&lt;springProperty scope=&quot;context&quot; name=&quot;logUrl&quot; source=&quot;logging.logstashHost&quot; resource=&quot;application-unittest.yml&quot;
                      defaultValue=&quot;myUrl:39290&quot;/&gt;
  </code></pre>
  <p>in my <code>logback-test.xml</code></p>
  <p>and use it like:</p>
  <pre><code>  &lt;appender name=&quot;myAppender&quot; class=&quot;net.logstash.logback.appender.LogstashTcpSocketAppender&quot;&gt;
          &lt;destination&gt;${logUrl}&lt;/destination&gt;
          &lt;keepAliveDuration&gt;5 minutes&lt;/keepAliveDuration&gt;
          &lt;encoder class=&quot;net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder&quot;&gt;
              &lt;providers&gt;
              &lt;/providers&gt;
          &lt;/encoder&gt;
      &lt;/appender&gt;
  </code></pre>
  <p>However this ${logUrl} is always undefined:</p>
  <blockquote>
  <p>logUrl_IS_UNDEFINED':</p>
  </blockquote>
  <p>Why isnt spring picking up the property? And why isnt defaultValue used? I tried to rename my <code>logback-test.xml</code> to <code>logback-test-spring.xml</code> or <code>logback-spring.xml</code> but my tests arent picking the configuration then.</p>
  <p>What is the way to fix it?</p>