raft: fsm_test: test_leader_transfer_lost_timeout_now
raft: fsm_test: test_leader_transfer_lost_timeout_now

3-node cluster (A, B, C). A is initially elected a leader.
The leader adds a new configuration entry, that removes it from the
cluster (B, C).

Wait up until the former leader commits the new configuration and starts
leader transfer procedure, sending out the `timeout_now` message to
one of the remaining nodes. But at that point it haven't received it yet.

Lose this message and verify that the rest of the cluster (B, C)
can make progress and elect a new leader.

Tests: unit(dev, debug)

Signed-off-by: Pavel Solodovnikov <2cf5887fafb117b7ff3e29b9720a7305c3313494@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla