Fixed TryFinishingBlow attempting to return by parameter reference.
The new luabind fails with a by_reference to by_value check. Using
a pointer accomplishes the same goal, but bypasses this issue.
There is cases where we need to get a random client, but
GetRandomClient() is not sufficient enough due to complex predicates
required on what tells us is a valid client. This way we can just loop
over a shuffled list and verify a client is valid instead of multiple
GetRandomClient() calls.
