We currently only update the failure detector for a node when a higher
version of application state is received. Since gossip syn messages do
not contain application state, so this means we do not update the
failure detector upon receiving gossip syn messages, even if a message
from peer node is received which implies the peer node is alive.
This patch relaxes the failure detector update rule to update the
failure detector for the sender of gossip messages directly.
Refs #8296Closes#8476
9ea57dff21