Task suspension

[nicoloboschi]

JIRA: https://dev.majordodo.org/jira/browse/MAJ-3

Reporter: eolivelli @eolivelli

Sometimes a task needs to wait for a long time while accessing other slow or remote resources, such asinchronous batch-style services.

This feature is the ability for a task to request the broker to be restarted after an interval of time.
Basically it is to be handled as a temporary failure of the task with the usual re-try policcy, but:

• the status of the task should not be "waiting", but somthing like "suspended"
• the number of attempts should not be increased
• the execution is to be scheduled on the future (see MAJ-2)