Refactor StartcodeAgnosticServerName so it doesn't extend ServerName

Follow up jira to address toffer's review comments @ https://reviews.apache.org/r/53242/. /cc devaraj.

Apart from sharing a lot of functionality as ServerName it seems there is no need to be a subclass. In fact it is prolly not good design to do so as it may cause unwanted mixups for the user. (ie both instances in the same collection). Since this is functionally correct. We can address this in a separate jira. Prolly something we should do before we pull in the next jira.