Prior to the 2022g import, tzloadbody() returned -1 on error. Now it
returns an errno code. When I updated the time zone change detection
logic to match, I improperly returned errno in all cases, which means
that if the time zone file has not changed since we last loaded it,
tzloadbody() returns a random errno value instead of 0.

Fixes: bc42155199b5
MFC after: 1 week
Sponsored by: Klara, Inc.
Sponsored by: NetApp, Inc.