Previously, the openstack::compute class did not pass the
ovs_enable_tunneling parameter. Now that the module supports
Provider Networking, ovs_enable_tunneling must be configurable
to allow users to disable tunneling when using VLAN networking.
Adds parameter ovs_enable_tunneling, which defaults to true.
Change-Id: I73d659d5857b71448e5d5d0ddc65fa79ce8f1d95