honour 'vlan_interface' configuration stanza in `vmware' puppet class

- when vCenter is used with nova-network (VlanManager) 'vlan_interface'
  configuration option is available in [vmware] section
- introduce new parameter 'vlan_interface' for `vmware' and
  `vmware::controller' puppet classes
- if 'vlan_interface' is defined and not empty write appropirate string
  to nova-compute (not nova-network) configuration file
  (/etc/nova/nova-compute.conf)

Change-Id: I5e7e4007c112516f039f65c7ed5f8d11d676eee9
Closes-bug: #1397293
Merge "honour 'vlan_interface' configuration stanza in `vmware' puppet class"