Fix OpendaylightApiNetwork key naming
Fix OpendaylightApiNetwork key naming

This captialization won't work with the CamelCase to snake_case
conversion we do, as the required name is opendaylight_api_network

Adds some clarification to the ServiceNetMap description to hopefully
avoid future confusion.

Change-Id: Ife04ee2185e81009ebef55ad521aef799251e002
Closes-Bug: #1629408
(cherry picked from commit eaa385f3b0460497d04845a71ad0a16be4c435fe)

trozet/opnfv-tht,trozet/opnfv-tht,trozet/opnfv-tht