Update cluster.sh
Update cluster.sh

Made cluster.sh script POSIX compatible.
tombujok/hazelcast,emrahkocaman/hazelcast,dbrimley/hazelcast,juanavelez/hazelcast,tufangorel/hazelcast,mdogan/hazelcast,dsukhoroslov/hazelcast,mesutcelik/hazelcast,tkountis/hazelcast,mdogan/hazelcast,mdogan/hazelcast,lmjacksoniii/hazelcast,tkountis/hazelcast,dsukhoroslov/hazelcast,dbrimley/hazelcast,juanavelez/hazelcast,emre-aydin/hazelcast,dbrimley/hazelcast,Donnerbart/hazelcast,tombujok/hazelcast,emre-aydin/hazelcast,emre-aydin/hazelcast,Donnerbart/hazelcast,tufangorel/hazelcast,mesutcelik/hazelcast,lmjacksoniii/hazelcast,Donnerbart/hazelcast,tufangorel/hazelcast,emrahkocaman/hazelcast,tkountis/hazelcast,mesutcelik/hazelcast