Don't restart SystemUI in TestHarness mode.

Log the name of the flag that is causing restarts.

Also, we weren't copying old overrriden-id's into the new
overridden-names. Fix that.

Fixes: 267753212
Test: atest SystemUITests and some manual flag flipping.
Change-Id: I7df265a54e657453c664c3d77987ee498c1c97cd