core: Remove GetAllIdsFromExportDomainQuery

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

This patch removes the following:
1. The GetAllIdsFromExportDomainQuery class
2. The GetAllIdsFromExportDomain constant representing it in
   VdcQueryType
3. The GetVmsListVDSCommand class which was only used by
   this query.
4. The GetVmsList constant representing it in
   VDSCommandType.
5. The getVmsList(String, String)  method in
   IIrsServer/IrsServerWrapper, which was only used
   by GetVmsListVDSCommand.
6. The GetVmsListReturnForXmlRpc class which was only used by
   GetVmsListVDSCommand.

Change-Id: Id6c384ccbb317f67afb4d0fc13373dd6c7671f93
Signed-off-by: Allon Mureinik <amureini@redhat.com>