Index Rollup schedule start time issue

[ikibo]

Description
When creating a Rollup via Rollup create PAI and defining interval schedule, the Rollup gets created with schedule.start_time equal to the current time, but not with the time defined in the create request.

Steps to reproduce:

1. Create a Rollup via create API with defined interval schedule and schedule.start_time
2. The returned created Rollup gets created with schedule.start_time equal to current time (time of request execution). Not the time defined in step 1.
3. Get he created Rollup by the get API and it schedule.start_time is not equal to time defined in step 1.

Expected behavior:
A Rollup must be created with schedule.start_time defined in step 1.

What is your host/environment?

• OS: macOS
• Version: 14.1
• Plugins: job schedler, index management

Additional context
this issue is similar to the issue #801

[ikibo]

@bowenlan-amzn, plz, assign me to this one