DO NOT MERGE Start SetupWizard ExitActivity on gear reversal

* Start SetupWizard's ExitActivity on a gear change to reverse
- change from the home intent to starting the exit activity
* Start the ExitActivity if the gear is already in reverse when starting

Bug: 151109459
Test: TreeHugger
Signed-off-by: Julius D'souza <jdsouza@google.com>
Change-Id: Ia93d7b3caeea2ec7d7c7f02940f45d0c2a5d9aec
Merged-In: Ia93d7b3caeea2ec7d7c7f02940f45d0c2a5d9aec