Add 3.4. to clusterLevels and supportedENGINEs.

Add version 3.4. to clusterLevels and supportedENGINEs, returned
by VDSM as part of engine calling getCapabilities. This allows
to test 3.4 specific features from engine.

Change-Id: Iceada517e2cd85a35264f9c60fc6f121f559f40d
Signed-off-by: ndarshan <dnarayan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21443
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>