etcdserver/raft: remove msgDenied, removedNodes, shouldStop

The future plan is to do all these in etcdserver level.

raft/node.go

@@ -35,11 +35,9 @@ var (
 // SoftState provides state that is useful for logging and debugging.
 // The state is volatile and does not need to be persisted to the WAL.
 type SoftState struct {
-	Lead         uint64
-	RaftState    StateType
-	Nodes        []uint64
-	RemovedNodes []uint64
-	ShouldStop   bool
+	Lead      uint64
+	RaftState StateType
+	Nodes     []uint64
 }
 
 func (a *SoftState) equal(b *SoftState) bool {