This is a followup to "Use messaging notifications transport
instead of default" (Ic72fd658fe9b35d39cc3d7da2e4b9fe3454edfba).
The use of NOTIFICATION_TRANSPORT should be global. A unit
test is added; it fails if the variable isn't global.
A typo was addressed in the release notes.
Change-Id: Ie303d79aba893b36a7aecb29c0ff2703f742146e