Refactor print_vgpu_conf into two functions

Signed-off-by: John Else <john.else@citrix.com>
Print the new psubdev_id on test failure

Signed-off-by: John Else <john.else@citrix.com>
Add tests of the vgpu config parser

Includes a couple of example config files.

Signed-off-by: John Else <john.else@citrix.com>