Revert "Merge pull request #1476 from yangdongsheng/pci_passthrough"

This reverts commit 7aed6c863c34b2df94dbd18bbddc58dbcac4eedd, reversing
changes made to 71a43c211d795345cc244cec2feda6b1f9ed90e0.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>

Conflicts:
	virttest/utils_test/libvirt.py