core: clear numa data that causes parsing error

In change 875214c4, numa node distance field is parsed
and persist differently, so in order to avoid parsing exception
this fix clears the data, and it will be filled in next iteration
of getVdsCaps.

Change-Id: I38bf5bb45199b9151d8a88667fe8b2de4b614209
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>