Commit Briefs
don't let the net process stick around
flush the net ibuf too
flush imsg buffer before quitting
this ensures that all the pending messages, such as the two IMSG_QUIT, but limiting to them, are actually sent. This unbreaks save_session too.
fix certificate mismatch after load_previous_page and proxy
load_previous_page calls directly do_load_url, where the proxy reset happens in load_url.