[ftxtest] add support to get swarming task id from `build.Infra.Backend`
with the upcoming Buildbucket's swarming -> backend migration, the swarming task info in `build.Infra.Swarming` will be moved to `build.Infra.Backend` instead.
This CL will make sure the swarming task id can be retrieved from both builds running on raw swarming and backend.
Bug: 328639287, 326482303
Change-Id: I813798438d22d5be4c25178641d5ed2881b54d52
Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/infra/+/1005538
Reviewed-by: Vinicius Felizardo <felizardo@google.com>
Commit-Queue: Chan Li <chanli@google.com>
1 file changed