stunnel component is not used, don't extend it.

stack/erp5/buildout.cfg

@@ -48,7 +48,6 @@ extends =
   ../../component/python-2.7/buildout.cfg
   ../../component/python-ldap-python/buildout.cfg
   ../../component/rdiff-backup/buildout.cfg
-  ../../component/stunnel/buildout.cfg
   ../../component/subversion/buildout.cfg
   ../../component/tesseract/buildout.cfg
   ../../component/varnish/buildout.cfg
@@ -77,7 +76,6 @@ parts =
   memcached
   haproxy
   varnish-3.0
-  stunnel
   w3m
   poppler
   libpng