Only restart SystemUI when Server Flags actually change.

DeviceConfig is alerting us to all server pushes (pulls?). Even if
the flags is checking on aren't actually changing.

This CL ensures we only restart if the flag value has actually
changed.

Fixes: 272780732
Test: atest SystemUITests
Change-Id: I3571d210885472dc69f50c76922a89733f1a5d83
6 files changed