Add ceph_config ini helper

* add a ini_file helper as ceph_config.
* set the seperator as ' = ' in order to be the same as ceph-deploy
* add path param so that seperator can be easily tested.
** also allows for users to change the default path if desired.
* add test case to prove spacing around seperator.
* add simple test case to ensure type works.

Closes-bug: #1243852
Change-Id: I0f3bb41d75d48d8af3b5b7cfb7768c4d3de2c002