Update neutron content for Juno

I updated the neutron content in the installation guide for Juno
as follows:

1) Explicitly install ipset package on network and compute nodes
   as a workaround for potential dependency issues. See LP bug
   #1369386 and patch #111877.
2) Configure the ML2 plug-in to use ipset.

Change-Id: Ie986a3114ee778f97359b53d58ac805100575a37
Merge "Update neutron content for Juno"