GS-10935 Code that creates both GatewayProcessingUnit and Gateway moved from DiscoveryService to DefaultAdmin, in such way we will prevent that method getProcessingUnit() of GatewayProcessingUnit returns null.

git-svn-id: svn://pc-lab14/SVN/xap/trunk/openspaces@137140 eb64e737-3616-4df0-8941-5ee2ae88103d