core: Remove unused GetVGInfoQuery

Removed the unused GetVGInfoiQuery.
This patch removes the following:
1. The unused GetVGInfoQuery class.
2. The VGQueryParameterBase class only used by GetVGInfoQuery.
3. The GetVGInfo constant in VdcQueryType corresponding to the removed
   class.

Change-Id: I1e43d685ffd2c0664094c024f883c853d7edfc75
Signed-off-by: Allon Mureinik <amureini@redhat.com>