Doesn't reconnect to staticnodes after connection failure or disconnect

[jlokier]

The --staticnodes options is most useful for nodes that are willing to provide service. But occasionally, Geth doesn't accept a connection even if we are "trusted node" for Geth. It's just luck; the Geth would be willing, but at that moment it didn't have capacity.

Currently, after a connection failure or disconnect, Nimbus-eth1 stays disconnected from its --staticnodes. When this hapens, Nimbus-eth1 should reconnect after a short time, on the assumption that's what --staticnodes is for.

This is especially important when we aren't syncing to anything else and have discovery turned off, and in that state Nimbus-eth1 becomes kind of useless, reporting zero peers in a loop.