prevent pool from double scaling up, reduce latency

lib/gat/handlers/pool/pooler.go

lib/gat/handlers/pool/poolers/lifo/factory.go

lib/gat/handlers/pool/poolers/lifo/pooler.go

lib/gat/handlers/pool/poolers/rob/factory.go

lib/gat/handlers/pool/poolers/rob/pooler.go

lib/gat/handlers/pool/spool/pool.go

lib/rob/schedulers/v3/scheduler.go