[keyserver] Ignore promise rejections from state check mechanism

Summary:
The unused-promise Lint identified an issue here. Since we don't handle promise rejections from this code, there is a risk of crashing the keyserver.

To avoid that, in this diff I wrap the call with ignorePromiseRejections.

Depends on D10181

Test Plan: Flow

Reviewers: michal

Reviewed By: michal

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D10182