tp-libvirt: Add provider libs

The module virsh is heavily modified by libvirt tests,
yet it is used by core virt-test functionality, although
a limited subset of APIs.

From now on, new virsh additions should be done in
the virsh provider lib, and tests themselves should
use provider.virsh instead of virttest.virsh.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
tp-libvirt: Reorganize imports

Reorganize imports for all libvirt tests, and make use of the
new provider.virsh library.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #12 from autotest/provider-libs

Provider libs