Flight mode async

This change includes a number of changes to urfkill in order to fix a few longstanding critical flight-mode bugs, namely:

https://bugs.launchpad.net/ubuntu/+source/urfkill/+bug/1321627
https://bugs.launchpad.net/ubuntu/+source/urfkill/+bug/1339794
https://bugs.launchpad.net/ubuntu/+source/urfkill/+bug/1354716
https://bugs.launchpad.net/ubuntu/+source/urfkill/+bug/1354716


Well, if type >= NUM_RKILL_TYPES someone compiled the code against a newer kernel that adds a new type, or the kernel is just plain broken.  This should *never* happen on a production device running Ubuntu.  The previous code had no log message at all, so I went mid-way and just added the warning.  I think the g_assert () is really warranted, but let's hold off and try to get this thing out the door first.