Schedules a stability message to be mcast after a random number of milliseconds (range 1-5 secs).
The reason for waiting a random amount of time is that, in the worst case, all members receive a
STABLE_GOSSIP message from the last outstanding member at the same time and would therefore mcast the
STABILITY message at the same time too. To avoid this, each member waits random N msecs. If, before N
elapses, some other member sent the STABILITY message, we just cancel our own message. If, during
waiting for N msecs to send STABILITY message S1, another STABILITY message S2 is to be sent, we just