Test matrixElevatedAgend.start function

[alstojanovic]

The following code threw a rejected promise with undefined reject reason:
service/src/services/matrix/agent

const startComplete = new Promise<void>((resolve, reject) => {
      const subscription = this.eventDispatcher.syncMonitor.subscribe(
        ({ oldSyncState, syncState }) => {
          if (syncState === 'SYNCING' && oldSyncState !== 'SYNCING') {
            subscription.unsubscribe();
            resolve();
          } else if (syncState === 'ERROR') {
            reject();
          }
        }
      );
    });

[ ] Add observability and if possibly tests that will allow us to know if the matrix adapter service is running correctly.