Poll cold start fix

[jnunemaker]

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It's possible if using an adapter that doesn't retain state that a feature could be checked before the first background thread sync finishes. If this happens flipper thinks no features are enabled. That's not good. So let's avoid that by forcing a sync in the main thread.

Should we rescue around the sync and warn? Probably?

[jnunemaker]

Looks like I have failures to deal with first because the tests don't like doing the sync.