Better error message for no host or client.conf.string

[javier]

I had a typo in which I was passing the client.conf.string= property, with a trailing equal sign. Of course I had an error message saying this

{"error_code":500,"message":"Either 'client.conf.string' or 'host' must be set."

I misinterpreted the message and I thought I was passing both the client.conf.string and host properties, and I was trying to see why host was being used. After a while I noticed my error. This might be only me, but maybe rewording the message to say that None of the properties have been configured would make things easier.

Thanks!

[jerrinot]

@javier: I am considering to not talk about host at all. Since new deployments should use the client conf string anyway. WDYT?