core: Remove unused IsUserPowerUserOrAboveQuery

Removed the IsUserPowerUserOrAboveQuery and its corresponding constant
in VdcQueryType since it is not used anywhere in the code.

Change-Id: I82982b3a6950339a9c3623078f4bd0e36c9d8f6f
Signed-off-by: Allon Mureinik <amureini@redhat.com>