Remove param validation if enable_ovs_agent=false

Currently the controller module assumes that the
OVS agent is always configured when the neutron
service is configured. This patch ensures that
when OVS agent is not enabled, we do not require
OVS agent specific params to be set.

Change-Id: Id3e601841f2c962dbe9a142c4bdfe80b1a9fd4a7
Merge git://github.com/puppetlabs/puppetlabs-openstack