If scheduler.password is wrong, then the reporting module will quickly lock your admin account

See TRUNK-3272.

Proposed quick solution:

• store "last failed login timestamp" as a static variable on AbstractReportsTask
• in the authenticate() method, if we're within 5 minutes of the last failed login, then do not try to log in again; instead log a warning

(Unfortunately "5 minutes", or rather 300000 ms, is hardcoded in HibernateContextDAO in core, so we're stuck hardcoding that as well.)