[CBM] Increase staging directory lockfile polling

What is the problem?
If we cannot get the staging directory lock we currently poll until we can, for at most a minute. This is so that if a short-lived command that does not lock the remote archive (e.g. info) is running then we do not fail a backup.

Unfortunately staging directory population can take far longer than a minute which means info may not be that short-lived.

What is the solution?
Until we limit the number of backups (MB-50645) or manage to improve population speed a lot (MB-60677) we should poll for a little longer. I suggest five minutes