grpcproxy: use new lease interface

proxy/grpcproxy/lease.go

@@ -255,10 +255,7 @@ func (lps *leaseProxyStream) recvLoop() error {
 func (lps *leaseProxyStream) keepAliveLoop(leaseID int64, neededResps *atomicCounter) error {
 	cctx, ccancel := context.WithCancel(lps.ctx)
 	defer ccancel()
-	respc, err := lps.lessor.KeepAlive(cctx, clientv3.LeaseID(leaseID))
-	if err != nil {
-		return err
-	}
+	respc := lps.lessor.KeepAlive(cctx, clientv3.LeaseID(leaseID))
 	// ticker expires when loop hasn't received keepalive within TTL
 	var ticker <-chan time.Time
 	for {
@@ -276,7 +273,7 @@ func (lps *leaseProxyStream) keepAliveLoop(leaseID int64, neededResps *atomicCou
 			lps.mu.Unlock()
 			return nil
 		case rp, ok := <-respc:
-			if !ok {
+			if !ok || rp.Err != nil {
 				lps.mu.Lock()
 				delete(lps.keepAliveLeases, leaseID)
 				lps.mu.Unlock()