[sheepdog] [PATCH] add early test for xattr support

[Dietmar Maurer]

> > Should we check this in farm_init() since only farm uses extended
> > attributes?  Currently, there is no other storage driver than farm and
> > the check will be executed in either way, though.
> >
> 
> I agree. And I also think that for a gateway-only node, there isn't need to call
> farm_init() even case gateway-only node doesn't need backend store.

BTW, the current code swallows most error messages at startup, because daemon() closes stderr.

- Dietmar