Provide host controller name via org.jboss.as.server.ServerEnvironment

The org.jboss.as.server.ServerEnvironment provides information about a given server instance such as the server name and various system directories, properties, etc. But, it does not contain the host controller name. Having the host controller name would allow a submodule to be able to understand its location within a domain.

If running standalone, the value would be 'null'