Document how to deal with round-robin host names
In #39 (and a few times before), we see potential problems with JupyterLab running on a host that has been selected from a round robin IP like:
$ host nesh-fe.rz.uni-kiel.de
nesh-fe.rz.uni-kiel.de has address 134.245.3.14
nesh-fe.rz.uni-kiel.de has address 134.245.3.13
nesh-fe.rz.uni-kiel.de has address 134.245.3.15
$ host nesh-fe.rz.uni-kiel.de | awk '{print $4}' | xargs -n1 host
13.3.245.134.in-addr.arpa domain name pointer nesh-fe1.rz.uni-kiel.de.
14.3.245.134.in-addr.arpa domain name pointer nesh-fe2.rz.uni-kiel.de.
15.3.245.134.in-addr.arpa domain name pointer nesh-fe3.rz.uni-kiel.de.
As this can lead to difficult-to-debug intermittent problems, we should document and give a recommendation for how to deal with this.