DO NOT MERGE Debounce wifi country code Info

We're getting signals from the radio and it sometimes drops out for
a while.  This change will delay applying an empty country code
for 15sec but apply non-empty country codes immediately.  It uses a
sequence number so we only apply the most recent change, even if
it's delayed.

Also secures the wifi call to set the country code as we can't
allow apps to set it willy-nilly.

bug:11062898
Change-Id: I610039a833e26d4c5c8b7b9ac1b7546f3c83446a