virttest.libvirt_storage_unittest: Fix py 2.4 incompatible construct

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest/versionable_class_unittest: Fix reference to base_utils

That module no longer exists in autotest. The correct
import should be utils anyway.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest.qemu_devices: Use backport implementation of OrderedDict

This will make the qemu devices unittest to pass on
python 2.4 systems.

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