En 7301 fix boostrap from storage

[iulianpascalau]

• return the nodes config after starting from storage when calling Bootstrap()

Steps used in testing:

• connect to an existing testnet using StartInEpochEnabled = true in config.toml in metachain shard. Let it synchronize.
• gracefully close the node, wait a couple of minutes, change the setting StartInEpochEnabled = false in config.toml.
• start the node, the node should be able to catch-up and sync properly the chain. Without the fix, the node was not able to sync because it would have a wrong view of the network (the eligible/waiting list was the one of the epoch 0) and almost all headers would have been discarded by the interceptors saying: invalid signature.