Update seedHosts with every good new config

Previously core-io would not update the seed nodes once a good config
has been found, but rather the original one would be used. This worked fine
since openBucket attempts are usually made when the app starts and only
over time the config list would diverge if nodes are added/removed from
the cluster.

A recent modification to support Kubernetes deployments which in turn made
it impossible to resolve hostnames early lead to a regression.