core: Remove GetAllEventSubsribers

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

This patch removes the following:
1. The GetAllEventSubsribersQuery class.
2. The GetAllEventSubsribers constant representing
   it in VdcQueryType.
3. The getAll() method in EvetDAO, its
   implementation, test and underlying stored procedure, as this
   method was only used by the aforementioned query.

Change-Id: Ic49e45cfdec1b08d2688d1e33f62a32176510547
Signed-off-by: Allon Mureinik <amureini@redhat.com>