core: Handle NUMA preferred tune mode

This patch addresses 3 issues:
- 5892ef11 added NumaTuneMode to VmBase, so we need to update all
VmStatic elements (VM templates) that was added since.
- libvirt failure when running in preferred mode without specifying
numa nodes. Added validation to add/edit VM to fail command when preferred
numa tune set and there is no single VM node configured pinned to NUMA
node.

Change-Id: I637fb996d06e97d55bdd8309a668307cac8bb546
Bug-Url: https://bugzilla.redhat.com/1146445
Bug-Url: https://bugzilla.redhat.com/1147261
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>
core: avoid sending NUMA values if not specified

Currently NUMA Tune Mode is sent even if VM doesn't have
virtual NUMA nodes configured.

Change-Id: I306a3004861295a6743288e5ed3a70cfdd49398d
Bug-Url: https://bugzilla.redhat.com/1147261
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>