fix(LogWriteWatcher): stop open/close the logfile
fix(LogWriteWatcher): stop open/close the logfile

opening and closing the log file slows down the whole
process when there are large amount of output on the log

scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests