fix: Prevent uninitialized SDK warning in daemon mode.

[kinyoklion]

When using daemon mode a warning would be produced on variation calls that the SDK had not finished initialization. This situation doesn't apply to daemon mode where we only read from the persistent store. It is instead intended to apply to persistent store modes where the SDK is writing to the persistence and applies to evaluations between SDK startup and initialization being complete.

This change updates the null update process to immediately report that it is initialized.