batchlog_manager: Stop its instances on shutdown
batchlog_manager: Stop its instances on shutdown

It's now stopped (not sharded::stop(), but batchlog_manager::stop)
on plain drain, but plain shutdown leaves it running, so fill this
gap.

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

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