Allow ovs_enable_tunneling to be Passed Through

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
Merge "Allow ovs_enable_tunneling to be Passed Through"