core: Remove GetAllVmPools

GetAllVmPoolsQuery is not used anywhere in
the code, and hence should be removed.

This patch removes the following:
1. The GetAllVmPoolsQuery class
2. The GetAllVmPools constant representing
   it in VdcQueryType

Change-Id: I09730eba7e90bc1372569ca8389ff346c099aa23
Signed-off-by: Allon Mureinik <amureini@redhat.com>