Bug 44133: Cleanup how we do config

Document where a config variable should be added better
Carefully move around config variables. Refactor
unset_stopmobileredirect.js so it doesn't introduce another
unnecessary variable

Bug: 44133

Change-Id: I126aadd503d233247b783af7bc4fcf13070a1299
Merge "Bug 44133: Cleanup how we do config"