[FAB-1924]: Rework delivery client

Move ordering service delivery client management into
gossip service, this to be able to maintain single
connection to the ordering service. Moreover this to
be widely used after gossip based leader election
integrated.

Change-Id: Iea9a70a1d6ba82caa55716444c54f3ddbc19673b
Signed-off-by: Artem Barger <bartem@il.ibm.com>