[ofw] CA attribute system_image_guid

[Sean Hefty]

>The driver gets system_image_guid upon query_ca, but, as for now,
>doesn't return it to the caller .
>I can fix it.
>Why do you need this field ?
>Which more missing fields are of interest ?

I was comparing the output of libibverbs examples running on windows and linux
to identify bugs in my windows port.  I sent a follow up email with a couple of
other missing values, but on a scale from 1 to 10, I would list these as not
very important...

- Sean