lock_resolver: let getTxnStatusFromLock return error when backoff tim…

…eout (tikv#847)

Signed-off-by: zyguan <zhongyangguan@gmail.com>
Co-authored-by: disksing <i@disksing.com>

txnkv/txnlock/lock_resolver.go

@@ -696,6 +696,7 @@ func (lr *LockResolver) getTxnStatusFromLock(bo *retry.Backoffer, l *Lock, calle
 		// success before the primary region.
 		if err := bo.Backoff(retry.BoTxnNotFound, err); err != nil {
 			logutil.Logger(bo.GetCtx()).Warn("getTxnStatusFromLock backoff fail", zap.Error(err))
+			return TxnStatus{}, err
 		}
 	}
 }