In the current scenario, We check if a node being removed is normal
on the node initiating the removenode request. However, we don't have a
similar check on the topology coordinator. The node being removed could be
normal when we initiate the request, but it doesn't have to be normal when
the topology coordinator starts handling the request.
For example, the topology coordinator could have removed this node while handling
another removenode request that was added to the request queue earlier.
This commit intends to fix this issue by adding more checks in the enqueuing phase
and return errors for duplicate requests for node removal.
This PR fixes a bug. Hence we need to backport it.
Fixes: scylladb/scylladb#20271
(cherry picked from commit b25b8dccbd)
Closesscylladb/scylladb#20800
33b50a9d3a