[Observer] Log error when unable to connect to bootstrap node

[peterargue]

Problem Definition

Observers are configured with an Access node as the "bootstrap node", which is used to instantiate the node's DHT and start syncing blocks. Without this initial connection, the observer will fail to find other peers on the network.

Currently, if this node is offline or the address is incorrect, the observer fails to sync data, but doesn't have any obvious error messages indicating that the Access node is offline.

Proposed Solution

Add an error message when the observer fails to connect to the bootstrap node. This may require adding an explicit connection attempt since connections are handled by libp2p and the error messaging my not be easy to control.