This will allow services which need to be aware of Dauntless
firmware changes to be notified by an init script trigger on
that property.
Bug: 286433589
Test: manual
Build an image with this change, confirm that `getprop
vendor.nos.citadel.version` returns the current Dauntless
firmware version string.
Update the Dauntless firmware, confirm that the property value
changes to match.
Change-Id: I45ce87070ce2b6c9fff2c8119db50445b0e576b3
Signed-off-by: Bill Richardson <wfrichar@google.com>