Currently the replacing node sets the status as STATUS_UNKNOWN when it
starts gossip service for the first time before it sets the status to
HIBERNATE to start the replacing operation. This introduces the
following race:
1) Replacing node using the same IP address of the node to be replaced
starts gossip service without setting the gossip STATUS (will be seen as
STATUS_UNKNOWN by other nodes)
2) Replacing node waits for gossip to settle and learns status and
tokens of existing nodes
3) Replacing node announces the HIBERNATE STATUS.
After Step 1 and before Step 3, existing nodes will mark the replacing
node as UP, but haven't marked the replacing node as doing replacing
yet. As a result, the replacing node will not be excluded from the read
replicas and will be considered a target node to serve CQL reads.
To fix, we make the replacing node avoid responding echo message when it is not
ready.
Fixes#7312Closes#7714
c82250e0cf