etcdserver: process the scenaro of the last WAL record being partially synced to disk

We need to return io.ErrUnexpectedEOF in the error chain, so that
etcdserver can repair it automatically.

Backport https://github.com/etcd-io/etcd/pull/15068

Signed-off-by: Benjamin Wang <wachao@vmware.com>

server/etcdserver/storage.go

@@ -15,6 +15,7 @@
 package etcdserver
 
 import (
+	"errors"
 	"io"
 
 	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
@@ -100,7 +101,7 @@ func readWAL(lg *zap.Logger, waldir string, snap walpb.Snapshot, unsafeNoFsync b
 		if wmetadata, st, ents, err = w.ReadAll(); err != nil {
 			w.Close()
 			// we can only repair ErrUnexpectedEOF and we never repair twice.
-			if repaired || err != io.ErrUnexpectedEOF {
+			if repaired || !errors.Is(err, io.ErrUnexpectedEOF) {
 				lg.Fatal("failed to read WAL, cannot be repaired", zap.Error(err))
 			}
 			if !wal.Repair(lg, waldir) {