Currently deployment awareness listens to only topology description changed events, which does not cover the case when connected to a standalone instance. If a standalone server goes into an unknown state, the topology type remains as single according to the SDAM specification even though the server description becomes unknown.

Therefore, we must also listen to these events when connected in standalone mode and fire the same changes as the existing topology related events.

• Change https://github.com/10gen/compass-deployment-awareness/blob/master/src/stores/index.js to also listen to 'serverDescriptionChanged` events and trigger with an overwritten 'unknown' state instead of keeping the same 'single' type. The read state and write state stores should handle this accordingly.