When adding or deleting a subscription, we save the subscriptions via `KVSet`, and previously turned around to fetch those with `KVGet` before broadcasting to the client. On installations with a database replica, the second request might not hit the `master` database, and the update just effected might not be "seen".

Skip the `KVGet` and instead just use the information about the updated susbcriptions that we already have in hand when updating the client.

Fixes: #342

…s-race