Change some assertTrue to assertIsNotNone

Change checks for a valid object from assertTrue to assertIsNotNone
which seems closer to the intent.

Also rename a local variable from "next" (name clash with the
built in function) to "next_time".

Change-Id: Ie7a770c7ac41e7c38e7d50728a7c194e5afec0cd
Add service user and some keystone parameters to Solum config

Keystone middleware requires to know the location
of keystone service. This patch adds new user for
Solum service and prepares keystone configuration
in Solum's configuration file.
This patch also adds a dedicated cache folder for
keystone middleware.

Change-Id: I4c4a25ffedb5b414ee903b28990a87a1106f358c
Merge "Change some assertTrue to assertIsNotNone"
Merge "Add service user and some keystone parameters to Solum config"