Fail to CONVERT_TZ for invalid DateTime

[iosmanthus]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

> set sql_mode = 'ALLOW_INVALID_DATES'
> select CONVERT_TZ(CAST('2019-4-31 2:00:00' as DATETIME), 'America/New_York', 'Asia/Shanghai')

2. What did you expect to see?

mysql iosmanthus@(none):test> select CONVERT_TZ(CAST('2019-4-31 2:00:00' as DATETIME), 'America/New_York', 'Asia/Shanghai')                           
+----------------------------------------------------------------------------------------+
| CONVERT_TZ(CAST('2019-4-31 2:00:00' as DATETIME), 'America/New_York', 'Asia/Shanghai') |
+----------------------------------------------------------------------------------------+
| 2019-05-01 14:00:00                                                                    |

3. What did you see instead?

mysql root@127.0.0.1:test> select CONVERT_TZ(CAST('2019-4-31 2:00:00' as DATETIME), 'America/New_York', 'Asia/Shanghai')                              
(1292, "invalid time format: '{2019 4 31 2 0 0 0}'")

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

Release Version: v3.0.0-rc.1-71-g7deedf841-dirty
Git Commit Hash: 7deedf8418c5c7f6d68cc3f0ea785cd83fefd3a8
Git Branch: master
UTC Build Time: 2019-05-15 03:14:01
GoVersion: go version go1.12.4 linux/amd64
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e
Check Table Before Drop: false

[iosmanthus]

Relative issue:

• CONVERT_TZ should return NULL if its arguments are invalid. #11161

[seiya-annie]

bug caused by invalid value should be Moderate

[dveeden]

Related: #8311