In do_apply_state_locally, a race condition can occur if a task is
suspended at a preemption point while the node entry is not locked.
During this time, the host may be removed from _endpoint_state_map.
When the task resumes, this can lead to inserting an entry with an
empty host ID into the map, causing various errors, including a node
crash.
This change
1. adds a check after locking the map entry: if a gossip ACK update
does not contain a host ID, we verify that an entry with that host ID
still exists in the gossiper’s _endpoint_state_map.
2. Removes xfail from the test_gossiper_race test since the issue is now
fixed.
3. Adds exception handling in `do_shadow_round` to skip responses from
nodes that sent an empty host ID.
This re-applies the commit 13392a40d4 that
was reverted in 46aa59fe49, after fixing
the issues that caused the CI to fail.
Fixes: scylladb/scylladb#25702Fixes: scylladb/scylladb#25621
Ref: scylladb/scylla-enterprise#5613
(cherry picked from commit f08df7c9d7)
e157e8577e