Refresh signal cluster for airplane switch.

This fixes a bug where if Airplane mode on/off is the only icon
that is changing in the signal cluster (for example, someone on
a wifi-only device has wifi turned on in airplane mode, so wifi
icon is not changing), this will refresh the signal cluster.

Bug: 6531918
Change-Id: I7a440b84c9dfa0b300b81d14426b99fd48fad06c