Decouple discovery service names from sandesh module and service
names. Move back to using 'Collector', 'ApiServer', 'OpServer' as
discovery service names.
Closes-Bug: #1389359

Change-Id: Ic58137f5a443d29fb33438f1a402c0b74f96738b
Merge "Decouple discovery service names from sandesh module and service names. Move back to using 'Collector', 'ApiServer', 'OpServer' as discovery service names. Closes-Bug: #1389359"