server issues request to client for discard suspended workunit in response to heartbeat msg
remove unused code in client api
awe-client can receive and parse operation requests from server in hbmsg
awe-client can kill in-progress process after receive server's 'discard' request'
maintain stage info at client side and kill only workunit at 'worker' stage
Merge pull request #79 from wtangiit/master

awe-client can kill in-progress process based on server requests