Request layout if visiblity (thus, size) changes

When wifi or mobile icons update state, they sometimes decide to show /
hide themselves or subviews. When this happens, they need to call
requestLayout() so that StatusIconContainer puts them in the right spot.

Also always center the wifi/mobile icons.

Bug: 110286625
Test: enter demo mode, show wifi and lte, hide lte, show lte -> there
should be no overlapping

Change-Id: Iad49783ac119d9994f4378f5b98f1a5b18f80c5d