Synchronize MCE master radio state with connman OfflineMode property

If OfflineMode property is changed via connman, the mce master radio
state is changed accordingly and legacy mce radio state change signals
are broadcast.

If MCE master radio switch is toggled, the connman OfflineMode property
is changed accordingly.

The mce master radio state is preserved over reboots and mce restarts
and will take priority over the OfflineMode setting kept by connman.

If connman for any reason chooses not to obey OfflineMode property
change, mce will modify master radio state instead.