SSL for communication between neutron and rabbitmq

Currently, Neutron can not be configured via Puppet to communicate with
rabbitmq using SSL. Most other puppet component already have this feature.
This commit enable this feature for Neutron.

Change-Id: Ie7a6218733562c4e89302ced169db6c53efadcf0
Enable neutron server to be run in SSL mode

This commit allows one to specify ca, cert and key file
to run neutron server in SSL mode.

Change-Id: I90f36e7c465924105e6b8032909988286f3e5374
Add parameter to set veth MTU

In many applications (including in particular NFV), it is useful
to use jumbo frames on veth pairs.  The OVS agent has a setting
enabling the user to set the MTU on veth interfaces, but it is
currently not exposed as a parameter.  This patch exposes the
veth_mtu setting and adds rspec tests accordingly.

Change-Id: I7b211be29a5630874b1c56e79ca80667f96ce425