core: Settle log target if we're going to be closing all fds
    
    Whenever we're going to close all file descriptors, we tend to close
    the log and set it into open when needed mode. When this is done with
    the logging target set to LOG_TARGET_AUTO, we run into issues because
    for every logging call, we'll check if stderr is connected to the
    journal to determine where to send the logging message. This check
    obviously stops working when we close stderr, so we settle the log
    target before we do that so that we keep using the same logging
    target even after stderr is closed.