buildscripts: Add missing secondary_kube_context to xds LB tests (#9380)
buildscripts: Add missing secondary_kube_context to xds LB tests (#9380)

Secondary cluster was not activated for LB tests. This resulted in the failover test failing, as it relies on workloads running in different zones.

ref b/238226704
stanley-cheung/grpc-java,grpc/grpc-java,grpc/grpc-java,stanley-cheung/grpc-java,stanley-cheung/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,grpc/grpc-java