Set all folder states to InterruptingIdle in case they were Idle before.
Called during dc_maybe_network() to make sure that all_work_done()
returns false immediately after dc_maybe_network().
Set the connectivity to “Not connected” after a call to dc_maybe_network_lost().
If we did not do this, the connectivity would stay “Connected” for quite a long time
after maybe_network_lost() was called.