Always copy SignalIconState when keeping a reference

Defensively copy SignalIconState so that StatusBarWifiView and
StatusBarMobileView can properly detect changes to state.

Also don't do visibility changes if setting the same visibleState on
StatusBarWifiView.

Test: turn wifi on and off; verify that it goes away properly in status
bar
Fixes: 78353558
Fixes: 77738471
Fixes: 78050495
Fixes: 78163313

Change-Id: Ie9b9e05885c130c1ec6d6abb9d0567400df23e52