indicatorPeriod.update_actual_value does not update actual value for later periods

[gabemart]

Say we have period1 with update1. period1 has a baseline of 0 and update1 has a change value of +5.

Say we also have period2 which starts after period1, and period2 has update2 which has a change value of +1.

In this case, period1 has an actual_value of 5 and period2 has an actual_value of 6.

The problem happens when we edit update1 after we've already created update2. For example, if we change update1 from a +5 to a +6.

Currently, the actual_value of period2 remains at 6 - but update2 still has a change value of +1. The actual_value of period2 should be updated to 7.

The actual_value of period2 should be changed when we call update_actual_value on period1