Test: remove wait on events from multipleNodesShutdownNonMasterNodes

The test validates that minimum master node is honored after shutting down nodes. When nodes are restarted we may go through a couple of master election of a master is elected and  discovers some of the old nodes left before all new node have joined. Processing that node failure the master de-elects it self, which is fine because we will start a new master election. Test however runs a clusterHealth call with a  wait for event. This is implemented using a cluster state update task which fails when the master steps down. Longer term fix requires a rewrite of the cluster health API code but a quick fix is not check for events (not needed for this test).