Extract JGroups configuration into jgroups section

Until now all JGroups configuration was contained in the
peerInfo.jgroups subsection. This made sense if we would only use
JGroups for peer discovery. However, if we want to support message
transport over JGroups then we need a standalone [jgroups] section,
same like we have a standalone [http] section for REST based message
transport.

This change is a preparation for JGroups based message transport.

Change-Id: Ib8b831b524f69604effe59f50df221f4ec630b23
6 files changed