fix missing os. in os.popen. and clear the autoresume flags if the chroot is invalid...

fix missing os. in os.popen. and clear the autoresume flags if the chroot is invalid.  Fix SEEDCACHE unpack issue when needing to use tarball.

git-svn-id: svn+ssh://svn.gentoo.org/var/svnroot/catalyst/trunk@822 d1e1f19c-881f-0410-ab34-b69fee027534