Rest API: POST action with JSON data fails with `TypeError("'coroutine' object is not an iterator")`

[louis-nexthop]

Calling POST action with JSON data would fail with TypeError("'coroutine' object is not an iterator"):

root@bmc-oob:~# curl -s -X POST \
  -H "Content-Type: application/json" \
  -d "{\"action\":\"power-on\"}" \
  http://localhost:8080/api/sys/server
{"Information": {"reason": "TypeError(\"'coroutine' object is not an iterator\")"}, "Actions": [], "Resources": []}

This is because of the transition from aiohttp 2.3.10 -> aiohttp 3.0.0, where Request.json() no longer returns a generator-based coroutine (v2.3.10 vs v3.0.0).