NSX integration fixes

Actually, met me suggest this code, which will be less likely to break in case of future changes:

```ruby
pkgs = [ node[:neutron][:platform][:dhcp_agent_pkg], node[:neutron][:platform][:metadata_agent_pkg], node[:neutron][:platform][:metering_agent_pkg] ]
pkgs << node[:neutron][:platform][:l3_agent_pkg] unless node[:neutron][:networking_plugin] == "vmware"
```