Fix dumping of PSCSI storage objects

Wow, I guess this has never worked?

Add dump method, so PSCSI dev will be saved.

Unlike all others, PSCSI doesn't want wwn. Move wwn to subclass dump()
methods, from superclass.

Signed-off-by: Andy Grover <agrover@redhat.com>
Remove unused local variable

Signed-off-by: Andy Grover <agrover@redhat.com>