Change ldap pool validation to validate periodically instead of on checkout by default

By default on 2.5.30+, this would validate connections every 30 minutes.  You probably want to have it validate more often, e.g. every 5 minutes (milliseconds):

ldap.<connection name>.validateTimerPeriod = 300000

To revert to the previous behavior, add the following.

ldap.<connection name>.validateOnCheckOut = true