Juno neutron updates

The following changes are needed to get neutron functional in Juno.

* ipset needs to be enabled in the l3 agent securitygroup section.
* conntrack needs to be installed.
* iputils-arping needs to be installed.
* policy json needs to be updated.

This PR adds all of the required changes to neutron and resolves
issue: https://github.com/rcbops/ansible-lxc-rpc/issues/276

increased sync threads

Disabled l3_ha by default.

This feature was supposed to solve for built in l3_ha in juno.
Sadly the l3_ha features is only half baked and some very serious
side effects which are reminiscent of 4.2.2. In order to maintain
stability l3_ha should be an experimental feature and only enabled
by the user when done so deliberately.

added ha dhcp agents to networks automatically

ReAdded the ATT neutron L3 ha tool.

This commit readds the neutron l3 ha tool. The att l3 ha tool
was removed in favor of native neutron l3 ha. Sadly native neutron
l3 ha is a bit of hack and does not work 100% as expected.
Merge pull request #277 from cloudnull/juno-neutron-updates

Juno neutron updates