[oe] do_unpack broken

[Graeme Gregory]

Hi, it looks like the series of commits starting with

commit 5c8bfd6873939024d57278343035cfab0257bdb3
Author: Chris Larson <chris_larson at mentor.com>
Date:   Wed Mar 17 08:05:40 2010 -0700

    do_unpack: shift some responsibility around, clean things up

has broken do unpack, I am not able to build since these were pushed to
the tree.

| ERROR: Error in executing python function in: /home/dp/openembedded/org.openembedded.dev/recipes/qemu/qemu_0.12.3.bb
| ERROR: Exception:<type 'exceptions.TypeError'> Message:oe_unpack_file() got an unexpected keyword argument 'env'
| ERROR: Printing the environment of the function
| ERROR: 	0030:			destdir = os.path.join(workdir, *subdirs)
| ERROR: 	0031:			bb.mkdirhier(destdir)
| ERROR: 	0032:		else:
| ERROR: 	0033:			destdir = workdir
| ERROR: 	0034:		oe_unpack_file(local, destdir, env=env, **urldata.parm)
| ERROR: 	0035:
| ERROR: Function base_do_unpack failed

Graeme