Randomize ud-replicate sync moment

[Wouter van Bommel]

With the installation of this charm, a crontab entry is created with the following content:

# crontab for the replicate operation, 15 min cycle.
10,25,40,55 * * * * root if [ -x /usr/bin/ud-replicate ]; then /usr/bin/ud-replicate; fi

Which means that on all clouds we are syncing on exactly the same time. This will eventually lead to a ddos, so we should revise this and make it a bit smarter.

*/15 for the minutes would already make a difference, as then it will be started every 15 minutes from the first moment it got the config. (and it will become distributed due to the fact that we are never going to be able to install / update all clouds at the same time.

[Haw Loeung (hloeung)]

Not sure where this charm was forked from, the version IS normally uses has this:

| https://bazaar.launchpad.net/~canonical-sysadmins/canonical-is-charms/userdir-ldap/view/head:/hooks/hooks.py#L196

[Haw Loeung (hloeung)]

Which seems present in this charm as well. So I wonder if these installations are using this charm in the first place?

[Eric Chen (eric-chen)]

Moved to https://github.com/canonical/charm-userdir-ldap/issues/13