avocado.plugins.xunit: Add NL at the end of output.

Signed-off-by: NRuda Moura <rmoura@redhat.com>

avocado/plugins/xunit.py

@@ -47,6 +47,7 @@ class XmlResult(object):
         if filename is None:
             filename = self.output
         xml = '\n'.join(self.xml)
+        xml += '\n'
         if filename == '-':
             sys.stdout.write(xml)
         else: