host.xml host name should default to something unique

in a distribibuted domain environment (ie. typical production env.) host name in host.xml must be unique :

<host xmlns="urn:jboss:domain:1.1"
name="RichS">

otherwise we get a startup error. To avoid having to modify this config for all machines (could be 10^3), we need a way to default this to a unique id. One idea would be to have a UUID property generated from the host-ip + process-id. That would provide unique IDs across the domain and also allow multiple instances per machine.

In domain mode this really should be the default (ie. we shold always use the property in domain/configuration/host.xml).

Note : if we do use host-ip+process-id then the ID is going to be different every time the process start - that may be a problem in itself.