cmapi: add-node does not work right after the cmapi service is started

Build tested: 1.5.4-1 (Drone #587), cmapi (Drone #251)

In a script, I did:

sudo ./service.sh install
sudo systemctl start mariadb-columnstore-cmapi
curl -k -s -X PUT https://s3pm1:8640/cmapi/0.4.0/cluster/add-node \
--header 'Content-Type:application/json' \
--header "x-api-key:$MCSAPIKEY" \
--data '

{"timeout":120, "node": "s3pm1"}

' \

the add-node did not return anything. No node was added. I added a "sleep 10" after starting the mariadb-columnstore-cmapi, then the add-node command worked.

It seems that mariadb-columnstore-cmapi service returned to the system prompt before it is ready to take on commands.