raft: replication test: wait for log propagation
raft: replication test: wait for log propagation

Wait until entries propagate after adding and before changing leader
using the same code as done for partitioning.

This fixes occasional hangs in debug mode when a test switches to a
different leader without leaving enough time for full propagation.

Signed-off-by: Alejo Sanchez <004be06a28e38b437b038f9b5c0b9f5758b792e9@scylladb.com>

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