Description of problem:
Imagine the situation in which there are two tasks in a swimlane and they are assigned to different groups. If a user complete the first one, the engine will try to claim the second one for him. This operation will not be performed, which is correct behavior. However, PermissionDeniedException is present in the log.

Version-Release number of selected component (if applicable):
BPMS 6.0.2 CR2

Steps to Reproduce:
1. Create a new process with a swimlane and two tasks in it.
2. Assign the first task to one group and the second one to another.
3. Create a user who belongs to the group from the first task but not to the group from the second one.
4. Run the process and try to claim-start-complete the first task with the user you have just created.
5. See what will happen before you try to do anything with the second task.

Actual results:
PermissionDeniedException: http://pastebin.test.redhat.com/218851

Expected results:
No exception at all. The engine should not try to claim the task.

Additional info:
This is a residual effect of bug 997139.