(SERVER-218) Docs on SSL server cert change and virtual ips

This commit includes some documentation related to the issue discovered
in SERVER-207 - the JDK assertion made that the server certificate does
not change following a session resumption attempt and a renegotiation
attempted from servers behind a virtual ip address.
I think this sentence is confusing in its wording. I think it should probably read "For the case that a load balancer is sitting between the Puppet master and PuppetDB instances and a client connection is directed..."