ovbackup and ovpurgejournals fail to find files to purge if backup/journal directories are symlinks

ovbackup and ovpurgejournals use the "find" command internally to get a list of files to be purged. Currently, the first argument passed to find (the directory to look in) doesn't have a trailing slash on it. This works if the directory is a real directory, but fails if the directory is actually a symlink, because find interprets this to mean "search the symlink". Adding a trailing slash to the first argument forces find to interpret the argument as a directory in either case.