Show roaming icon in status bar.

This also refreshes the data type icon when the data
connection state changes, so it'll pick up network speed
changes (3G->4G, e.g.) that aren't accompanied by some other
radio state change.

Bug: 5278165
Bug: 5274807
Change-Id: Ic97252a9fb29bd3f2a927f6a57666809297ad60e