Make sure to check that the cb in open_auth is an array.
Make sure to check that the cb in open_auth is an array.

We were forgetting to do this before and thus caused a ruby
crash if the passed-in argument was not an array.

Signed-off-by: Chris Lalancette <60b62644009db6b194cc0445b64e9b27bb26433a@redhat.com>

pronix/ruby-libvirt,pronix/ruby-libvirt,pronix/ruby-libvirt