bring up chassisdb service on sonic switch according to the design in
Distributed Forwarding in VoQ Arch HLD
Signed-off-by: Honggang Xu <hxu@arista.com>
**- Why I did it**
To bring up new ChassisDB service in sonic as designed in ['Distributed forwarding in a VOQ architecture HLD' ](90c1289eaf/doc/chassis/architecture.md).
**- How I did it**
Implement the section 2.3.1 Global DB Organization of the VOQ architecture HLD.
**- How to verify it**
ChassisDB service won't start without chassisdb.conf file on the existing platforms.
ChassisDB service is accessible with global.conf file in the distributed arichitecture.
Signed-off-by: Honggang Xu <hxu@arista.com>
