follow-up after fixing Nondeterministic DDL

[lance6716]

What did you do?

1. modification to job.ddls should be as late as possible
   

   tiflow/dm/syncer/syncer.go

   Lines 1332 to 1336 in 5a0452d

   	// set timezone
   	if ddlJob.timezone != "" {
   	s.timezoneLastTime = ddlJob.timezone
   	setTimezoneSQL := fmt.Sprintf("SET SESSION TIME_ZONE = '%s'", ddlJob.timezone)
   	ddlJob.ddls = append([]string{setTimezoneSQL}, ddlJob.ddls...)

to avoid interfering the logic between modification and using. Like

tiflow/dm/syncer/syncer.go

Line 1373 in 5a0452d

if len(ddlJob.ddls) == 0 {

2. there're too many warnings in log, we know in most of time there's no timezone information in status vars, so should not raise warning so frequently
   

   tiflow/dm/syncer/shardddl.go

   Line 158 in 5a0452d

   ddl.logger.Warn("found error when get timezone from binlog status_vars", zap.Error(err))

What did you expect to see?

No response

What did you see instead?

No response

Versions of the cluster

master

current status of DM cluster (execute query-status <task-name> in dmctl)

(paste current status of DM cluster here)