Assume n1 and n2 in a cluster with generation number g1, g2. The
cluster runs for more than 1 year (MAX_GENERATION_DIFFERENCE). When n1
reboots with generation g1' which is time based, n2 will see
g1' > g2 + MAX_GENERATION_DIFFERENCE and reject n1's gossip update.
To fix, check the generation drift with generation value this node would
get if this node were restarted.
This is a backport of CASSANDRA-10969.
Fixes#5164
(cherry picked from commit 0a52ecb6df)
921f8baf00