avocado.utils: Fix namespace availability problems

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.virt.qemu.cmdline: Fix docstrings

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.virt.qemu.devices.qcontainer: Fix wrong import

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado: Fix internal imports

That were making some of the namespaces not available.

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