One extra "s" in "messages", which was causing the following exception
when bulk updating patches with no patches selected:

  File "/srv/patchwork.freedesktop.org/lib/apache2/../../patchwork/views/__init__.py" in process_multiplepatch_form
    157.         context['messsages'] += ["No patches selected; nothing updated"]

  Exception Type: KeyError
  Exception Value: 'messsages'

Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>