core: Remove RegisterSearch and UnregisterSearch

Removed the RegisterSearch and UnregisterSearch constants from
VdcQueryType, as the corresponding queries no longer exists, making
these constants useless.

Change-Id: I2a1bb82d7096fa7cc6ef807739fec10cb44e1cbe
Signed-off-by: Allon Mureinik <amureini@redhat.com>