Do not exit nodetool repair when receiving JMX NOTIF_LOST

nodetool repair prints out 'Lost notification...' and exits when JMX NOTIF_LOST message is received. But we should not exit right away since that message just indicates some messages are lost because "they arrive so fast that they cannot be delivered to the remote client quickly enough" according to https://weblogs.java.net/blog/emcmanus/archive/2007/08/when_can_jmx_no.html. So we should just continue to listen to events until repair finishes or connection is really closed.