Plan mode of Rapid Board displays multiple sprints in progress

Tested on a JIRA 5.1 clean instance with GH 6.0.2

• Project A has a rapid board and has a sprint started called "Sprint A1".
• Project B has a rapid board and has a sprint started called "Sprint B1".
• An issue within Project B's sprint is cloned and moved into Project A.
• Since the Sprint field retains the value from the Project B sprint, but it now becomes a part of Project A, the Project A's Rapid Board shows "Sprint A1" and "Sprint B1" simultaneously.

We expect that the clone and the move operations should take this into account and either clear the previous sprint information or at least prompt the user about it.

Thanks!