Bootstrap nodes connection logging

[nkuba]

I'm afraid there may be something wrong with bootstrap rounds loggers, particularly the line logging all bootstrap attempts failed:

keep-core/pkg/net/libp2p/bootstrap.go

Line 197 in 6aa2f28

return fmt.Errorf("all bootstrap attempts failed")

I've noticed it a couple of times in the nodes that were connected to some of the bootstrap nodes. My understanding is that it should be logged only if a connection couldn't be established to any bootstrap node, but it may be logged differently.

We should revisit the bootstrap code and review all the loggers, so the logging messages are throwing errors only if it's really necessary (i.e. client failed to connect to any bootstrap node). Problems with connection to a particular bootstrap node should be logged as warnings.

We could also add a success message after establishing a connection to bootstrap nodes e.g. "established connection with 3 out of 5 bootstrap nodes".