Add random launch times

Even though there is no field test, is better to assume that
there will be some usage peaks.

In order to make this collection process sparse during
the week, just use a random contraint.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Replace return values for exceptions

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Collect on startup

Even though NM can trigger the collection process,
this can only happen once Sugar has started.

But, already configured connections are started before
sugar starts.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>