Decouple discovery service names from sandesh module and service
names. Move back to using 'Collector', 'ApiServer', 'OpServer' as
discovery service names. Added test case to ci sanity to verify
that webui is using ApiServer and OpServer service from discovery.
Closes-Bug: #1389359

Change-Id: I14255ee78e5084dd56ec005c6a0a2a1d8ede1086