fix emp->disarm adding

erroneous case: unit is damaged and has accumulated EMP damage, and then gets disarm damage.
the resulting disarm % should be (disarm % + current emp %)
currently this is (disarm % + (emp % * maxHP / hp))

example case:
unit is at 20% health and has 10% EMP damage, gets 1% disarm
result should be 11% disarm
currently it's 51% disarm (1% plus (10/20))
Merge pull request #303 from sprunk/patch-22

fix emp->disarm adding