Do not use os= in Config Reference

The Config Reference does not profile for the os variable and thus
all occurences of os=... are shown which leads to confusion. Add proper
wording for all examples.

Change-Id: I77c81b92e95d1b8737b507ea439a9622ebc3d6f1
Closes-Bug: #1232864
Merge "Do not use os= in Config Reference"