[0/10] Assorted cleanups (esp for fdt{get,put} tests)

As noted earlier, there were a few things I wasn't totally happy with
in the recently applied fdt{get,put} patches, mostly in the test code.
I had a look at cleaning up those problems today, which kind of
expanded into a whole bunch of little cleanups for tests and a few
other things.

So, here they all are.  Jon, please apply.