Ticket 47451 - Running a plugin task can crash the server
Bug Description: When a plugin task completes it attempts to update a counter,
but the wrong structure is accessed which can lead to a crash.
Fix Description: When creating a new task, make sure to store the plugin structure,
not the pblock in the task structure.
https://fedorahosted.org/389/ticket/47451
Reviewed by: rmeggins(Thanks!)
(cherry picked from commit 0e0848a8385463532d53db94c0c8cae912c30eb4)