[BUG] Rebase exception states not in UTC but timezone is Etc/UTC

[jlowe]

Saw a failure in a nightly build:

06:50:57    "error":"Job aborted due to stage failure.\nCaused by: ExecutionException: java.lang.UnsupportedOperationException: LEGACY datetime rebase mode is only supported for files written in UTC timezone. Actual file timezone: Etc/UTC\nCaused by: UnsupportedOperationException: LEGACY datetime rebase mode is only supported for files written in UTC timezone. Actual file timezone: Etc/UTC",

Looks like we're not normalizing the timezone loaded from the file before checking for equivalence to the UTC timezone.