fix dialyzer warnings in node watcher
fix dialyzer warnings in node watcher

addresses:
  L756: The created fun has no local return
  L757: The call erlang:apply(Mod::atom(),Func::atom(),nonempty_improper_list('undefined' | pid(),byte())) will
        never return since it differs in the 3rd argument from the success typing arguments:
        (atom() | tuple(),atom(),[any()])
  L757: Cons will produce an improper list since its 2nd argument is byte()
  L770: Function health_check_result/2 will never be called

Kyorai/riak_core