server: Add event bus bean as commented xml in META-INF core

This adds a spring bean xml to have EventBus for ACS, but the bean is commented
so the event bus service won't start by default. I'm adding this for any developer
who may want to hack on events and may use it just by uncommenting it and fixing
options.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>