watching actor node for terminate server
getpwuid_r's result did not memory leak..
bind() didnot needed
bind() wasn't needed in membership.cpp
exceptions should be catched in a watcher callback
all exception in zk callback should be catched before it penetrates C code area
some error message rewrite
we must not throw exception in zk callback
proper error message in watch_delete_actor()
exception in watch_delete_actor should be distinguishable
some refine of handling success flag
mixer thread should not terminate the server process
Merge pull request #499 from kumagi/feature/delete_from_actor_means_shutdown

Action that actor node is deleted from zookeeper should means server shutdown