Stop showing "No internet connection" when there is one.

In particular, even though the mobile data network isn't
routing packets (and therefore is not an internet
connection), we want to show the PLMN anyway:

  [MOBILE RSSI] Carrier  [WIFI RSSI] WiFi SSID

This change also improves the following cases:

 - Combines "No internet connection" from wifi and mobile
   into one single string in airplane mode:

     [AIRPLANE] No internet connection.

 - Removes "No internet connection" from the mobile string
   when wifi is on in airplane mode, making a nice compact
   display in this case:

     [AIRPLANE] [WIFI RSSI] WiFi SSID

Bug: 5903914
Change-Id: I477821d2c5e9922252dd6bcb3ed494c8c57d99b0