This patch adds new httpng.py which is a copy of http.py
from Salt 2017. It contains wait_for_successful_query method which
is needed in order to wait for init of OpenStack API interfaces
like Cinder API, Designate API, etc.
Change-Id: I5b4e526392df6dc0b9103a203937dbab31e0d301
Related-Prod: PROD-17170