core: pass MaxNumberOfSockets to create verb

in order to generate a correct topology xml-node for libvirt
VDSM needs also the MaxNumberOfSockets

Change-Id: I68368fdd40f0e43df18465c15faf2626789ee1c7
Bug-Url: https://bugzilla.redhat.com/1121295
Signed-off-by: Roy Golan <rgolan@redhat.com>