Add tie-breaking logic to NettyTransport.

Currently I do random wait in FastLeaderElection since if everybody sends the message at the same time, they will keep breaking the tie instead of establish the connection. I feel we should add the random wait logic to NettyTransport because it's hard for user of the transport to anticipate where this kind of situation might happen.

I guess the problem not just happen at one place, we just haven't found them. 

@m1ch1