Enhance SandeshConfig.get_default_options()
Enhance SandeshConfig.get_default_options()

Add ability to return default options per section. This allows
us to move all sandesh related options processing to a common
place.

Change-Id: I121c1c4505d335eaecd4284a4a87347eb665d310
Partial-Bug: #1679224

Juniper/contrail-sandesh,Juniper/contrail-sandesh,Juniper/contrail-sandesh,Juniper/contrail-sandesh