virt: qcontainer adds possibility to find device by params.

Allows to search specific device in qemu container by filter for
params. Created due to searching in the QStringDevices.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
qemu: Fix recreating VM defined by devices.

Some of qemu devices needs some kind of preparation before
start of qemu vm. Unfortunately there preparatory work are
done during creation of devices. For example network tap devices,
port redir, etc.
  It should be divided in some later patch.

Signed-off-by: Jiří Župka <jzupka@redhat.com>