wal: fix crc mismatch crash bug
wal: fix crc mismatch crash bug

gyuho/etcd,cockroachdb/etcd,coreos/etcd,cockroachdb/etcd,coreos/etcd,gyuho/etcd,rnaveiras/etcd,etcd-io/etcd,dannysauer/etcd,li-ang/etcd,ajityagaty/etcd,rnaveiras/etcd,mkumatag/etcd,mqliang/etcd,rnaveiras/etcd,li-ang/etcd,dannysauer/etcd,mqliang/etcd,ajityagaty/etcd,etcd-io/etcd,mkumatag/etcd,etcd-io/etcd,ajityagaty/etcd,mkumatag/etcd,mqliang/etcd