I really like this change if we are sure that __wt_epoch will never return an error when the system is in a running state. Phrasing my concern another way: the change means that any time __wt_epoch would return an error will now cause the storage engine to panic, which will cause a database-down for user applications. That's different to propagating out an error. The only case that seems mildly likely to cause problems is gettimeofday, which says:
Timezone (or something else) is invalid.
It's possible that error is only possible from settimeofday, but that's not clear from the man page.