No feedback while not being able to connect with Vaults

[fajfer]

When trying to connect to an instance with wrong token it just dissapears from the backend forever as there's no feedback related to it, there's also no clear way to reconnect to existing instance.

At the very least every instance from config should be visible even though backend is unable to fetch their health data

[fajfer]

If just one of the vaults fail we get:

Failed to load vault health

Internal Server Error