Before:

    "manager: check_if_startup_complete returns FALSE because of eth0"

Now:

    "manager: startup complete is waiting for device 'eth0' (autoactivate)"

Also, the logging line is now more a human readable sentence, but still
follows the same pattern as later

    "manager: startup complete"

Meaning: grepping for "startup complete" becomes more helpful because
one first finds the reasons why startup-complete is not yet reached,
followed by the moment when it is reached.