Spurious error log when setting feature flags at startup

[danxmoran]

Steps to reproduce:
Described in this comment.

Expected behavior:

1. Feature flags can be set via CLI, env, or config
2. When a feature flag is successfully set, no error log is displayed

Actual behavior:
Sometimes, attempts to override a feature flag are ignored.
Other times, the override succeeds, but a log message says it failed.