VGPU: Modify the example of vgpu white_list set
VGPU: Modify the example of vgpu white_list set

`enabled_vgpu_types` flag has been set in nova.conf to set enabled
vgpu type of current host. The example is wrong.
Modify the example to avoid mislead.

Change-Id: If7a150d4d28609cabeb5f513bbd134a969fca17c
Closes-Bug: #1746217

klmitch/nova,phenoxim/nova,rahulunair/nova,mahak/nova,gooddata/openstack-nova,mahak/nova,klmitch/nova,rahulunair/nova,openstack/nova,gooddata/openstack-nova,gooddata/openstack-nova,mikalstill/nova,klmitch/nova,mahak/nova,mikalstill/nova,openstack/nova,phenoxim/nova,gooddata/openstack-nova,openstack/nova,rahulunair/nova,klmitch/nova,mikalstill/nova