etcd: Add logs for unusual failures (#13460)

etcd operations, get/put/delete, should be logged when failed
with errors other than not found error. It will make it easier to
see connections issues from MinIO to etcd.

cmd/etcd.go

@@ -22,6 +22,7 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/minio/minio/internal/logger"
 	etcd "go.etcd.io/etcd/client/v3"
 )
 
@@ -47,6 +48,7 @@ func saveKeyEtcdWithTTL(ctx context.Context, client *etcd.Client, key string, da
 		return etcdErrToErr(err, client.Endpoints())
 	}
 	_, err = client.Put(timeoutCtx, key, string(data), etcd.WithLease(lease.ID))
+	logger.LogIf(ctx, err)
 	return etcdErrToErr(err, client.Endpoints())
 }
 
@@ -57,6 +59,7 @@ func saveKeyEtcd(ctx context.Context, client *etcd.Client, key string, data []by
 		return saveKeyEtcdWithTTL(ctx, client, key, data, opts[0].ttl)
 	}
 	_, err := client.Put(timeoutCtx, key, string(data))
+	logger.LogIf(ctx, err)
 	return etcdErrToErr(err, client.Endpoints())
 }
 
@@ -65,6 +68,7 @@ func deleteKeyEtcd(ctx context.Context, client *etcd.Client, key string) error {
 	defer cancel()
 
 	_, err := client.Delete(timeoutCtx, key)
+	logger.LogIf(ctx, err)
 	return etcdErrToErr(err, client.Endpoints())
 }
 
@@ -73,6 +77,7 @@ func readKeyEtcd(ctx context.Context, client *etcd.Client, key string) ([]byte,
 	defer cancel()
 	resp, err := client.Get(timeoutCtx, key)
 	if err != nil {
+		logger.LogIf(ctx, err)
 		return nil, etcdErrToErr(err, client.Endpoints())
 	}
 	if resp.Count == 0 {