When the node behind bch-api goes down, fulcrum and bch-api continue to function although they gradually get out of sync. This prevents the usual error throwing which causes the backends to switch.

This diff performs a node API check each update cycle. If the node is unavailable, the backend will switch.

Make sure kingbch.com node is down
npm start
Observe that the app immediately switches to the other backend
Start kingbch.com node
Observe that the app works okay