[Fuego] Extra Block Device should be specified for "fs_ext4" and "fs_readonly" tests

[Bird, Timothy]

> -----Original Message-----
> From:  Liu, Wenlong on Monday, October 09, 2017 12:59 AM
> Tests named "fs_ext4" and "fs_readonly" in Functional.LTP need a big block
> device.
> So, "-z BIG_DEVICE" might be added when using "./runltp".
> 
> But, where should this variable($BIG_DEVICE) be added? The board file is a
> good choice?

Yes.  This could be put into the board file, or it could be put into a spec file.
Generally, the board file is preferred.  If there is a chance some other test might
need this variable, it also could access it, if it's defined in the board file.
> And there are still many other variables besides "BIG_DEVICE", like
> $RHOST/$HTTP_DOWNLOAD_DIR/etc, when doing network related tests.

These might be put in the board file, but these might be generic enough that
we should put them into some kind of Fuego global configuration.
I'm not sure exactly the usage, but it might be useful to put them into:
fuego-core/engine/overlays/base/base-params.fuegoclass.

Since Fuego by definition runs a web server (Jenkins), and guarantees
to have a network host running (the host machine), then it's possible we
may want to just point these to something running in our docker container.
That would be the same for all Fuego installations, which would make configuration
easier.

However, different testers may want to test with different RHOSTS or 
different HTTP_DOWNLOAD_DIRs, so it would probably be good to make
these configurable.  (Note that values in board files override values in
the base-params files.)

We will be defining a global configuration file for Fuego in a future Fuego
release (I'm hoping in 1.3).

If you can describe how these are used by the LTP sub-tests, we can
think about the  best place to define these test variables.  

Thanks,
 -- Tim