Removing default user/user account from Java client

[Andrew MacBean <an...@gmail.com>]

All,

On the basis of improving security and preventing flags being raised by
software scanning tools, I am proposing the removal of the
static/default/hard-coded use of "guest/guest" in the Java client.

Specifically this is within ConnectionSettings.java (inside the common
module) and although I have checked it is only used by the client, I want
to make sure that this will not impact others who may be currently relying
on it?

If you think you are, let me know, otherwise I will proceed to remove this.

--Andrew