common: Don't g_message() on normal bootup

This log message gets emitted even if we have nothing to do on
normal bootup.  This spew is now more visible due to
See https://bugs.freedesktop.org/show_bug.cgi?id=68559

By reducing debug output, we make it easier to spot actual errors.

https://bugzilla.gnome.org/show_bug.cgi?id=712813