Strategies are not refreshed

[Francisco Javier Díez]

1. Open this network: http://www.probmodelxml.org/networks/dan/DAN-decide-test.pgmx.

2. Display the optimal strategy ("S" button).

3. Change the cost of the therapy to -10.

4. Display the optimal strategy again. Now the optimal policy should be "Therapy = no" in all cases, but OpenMarkov still shows the policy computed in step 2.

5. Save and reopen the network. Now OpenMarkov shows the optimal strategy.

[Miguel Ángel Artaso Landa]

Duplicate of #195.