etcd-tester: match ErrTimeoutDueToLeaderFail

stresser in followers should retry when failure is injected to
their leader.

tools/functional-tester/etcd-tester/stresser.go

@@ -105,12 +105,22 @@ func (s *stresser) Stress() error {
 						// as well. We want to keep stressing until the cluster elects a
 						// new leader and start processing requests again.
 						shouldContinue = true
+
+					case etcdserver.ErrTimeoutDueToLeaderFail.Error():
+						// This retries when request is triggered at the same time as
+						// leader failure and follower nodes receive time out errors
+						// from losing their leader. Followers should retry to connect
+						// to the new leader.
+						shouldContinue = true
+
 					case etcdserver.ErrStopped.Error():
 						// one of the etcd nodes stopped from failure injection
 						shouldContinue = true
+
 					case transport.ErrConnClosing.Desc:
 						// server closed the transport (failure injected node)
 						shouldContinue = true
+
 					case rpctypes.ErrNotCapable.Error():
 						// capability check has not been done (in the beginning)
 						shouldContinue = true