[libmultipath] tweaks for IBM / SGI common hardware

[libmultipath] tweaks for IBM / SGI common hardware

here's a small update for the hardware table.

I've added a new controller (IBM DS4100), which uses the same controller
than SGI TPC. For a proper support I had to relax the checks in pp_tpc
slightly.

Secondly, it sets the FAILBACK for all machines supported by pp_tpc to
-FAILBACK_IMMEDIATE, as we cannot (yet) adjust the path setting. Hence
we need to switch back to the preferred path as soon as it becomes
available again.

Hannes Reinecke, Suse