Support staggering of drive tests

[weedy2887]

On the mailing list a best practise thread popped up asking about test cycles which brought us to DEVICESCAN and the staggering of these tests when you have many (4+) drives in a box.

A: If a user feeds something like "(O/../../(7|3)/00|S/../.././12|L/../../6/03|C/../../7/03)" to DEVICESCAN it should use best effort to not send that command to every drive at once. It should probably assume something like +30% of a drives reported test runtime before triggering another drive. OR maybe the schedule is in "every X days" and not "sun-sat" calendar weeks per say.

B: A sane default (one short test per day, one/two long test per week, one offline per week/month?) to be added commented of course to the default config file.

[Christian Franke]

r5117.

[Christian Franke]

Not actually automatic, because there is no easy way to handle all common cases.

It is configurable in the regexp. With above example:

(O/../../(7|3)/00|S/../.././12|L/../../6/03:005|C/../../7/03:001)

specifies a five hour delay per drive for Long self-tests and a one hour delay for Conveyance self-tests.

[Christian Franke]

With r5118, this regexp:

(O/../../(7|3)/00|S/../.././12|L/../../6/03:005-023|C/../../7/03:001)

limits delay for Long self-tests to 23 hours.