Job API not return correct appLaunchedTime

[Binyang2014]

Refer to

pai/src/rest-server/src/models/v2/job/k8s.js

Line 254 in 338f5a3

appLaunchedTime: new Date(framework.metadata.creationTimestamp).getTime(),

Currently appLaunchedTime equal to creationTimestamp. So it will include waiting time. We need to return correct appLaunchedTime. And it's better to return launchTime for each task. Then we can monitor the actually resource utilization for job and task.