[16.0] [FIX] fieldservice: schedule date methods

[brian10048]

Two separate, but similar bugs related to schedule dates.

1. Prior to this fix If scheduled_date_end is updated, it would set date_start. The correct field is scheduled_date_start
2. On order, update the scheduled_date_start, but do not update duration. Save record and scheduled_date_end was overwritten assuming a 0 duration

[OCA-git-bot]

Hi @max3903, @wolfhall, some modules you are maintaining are being modified, check this out!

[dreispt]

/ocabot merge patch

[OCA-git-bot]

Hey, thanks for contributing! Proceeding to merge this for you. Prepared branch 16.0-ocabot-merge-pr-1194-by-dreispt-bump-patch, awaiting test results.

[OCA-git-bot]

Congratulations, your PR was merged at e4ab70d607aff0f9f9aec826c4e3e54d775d7d01. Thanks a lot for contributing to OCA. ❤️