add missing lxml-python egg

stack/monitor/buildout.cfg

@@ -8,6 +8,7 @@ extends =
   ../../component/openssl/buildout.cfg
   ../../component/logrotate/buildout.cfg
   ../../component/gzip/buildout.cfg
+  ../../component/lxml-python/buildout.cfg
 
 parts =
   slapos-cookbook
@@ -36,6 +37,7 @@ on-update = true
 [monitor-eggs]
 recipe = zc.recipe.egg
 eggs =
+  ${lxml-python:egg}
   plone.recipe.command
   collective.recipe.template
   cns.recipe.symlink