Fix cleaning of old files via ftp

[akupchanko]

We don't need to join the path to filename, received by ftp.nlst(path), because we get full path from ftp
And, as example, instead of removing mysqldump/postfixadmin/mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1443.sql.gz we should remove mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1443.sql.gz

Uploading FTP_SERVER:mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1445.sql.gz via FTP
Sending /var/astrails-safe/mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1445.sql.gz to mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1445.sql.gz
...done
listing files: FTP_SERVER:mysqldump/postfixadmin/mysqldump-postfixadmin.*
mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1443.sql.gz
mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1445.sql.gz
mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1444.sql.gz
removing ftp file FTP_SERVER:mysqldump/postfixadmin/mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1443.sql.gz
/usr/lib/ruby/1.9.1/net/ftp.rb:300:in `getresp': 550 mysqldump/postfixadmin/mysqldump/postfixadmin/mysqldump-postfixadmin.131026-1443.sql.gz: No such file or directory (Net::FTPPermError)
    from /usr/lib/ruby/1.9.1/net/ftp.rb:325:in `block in sendcmd'
    from /usr/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
    from /usr/lib/ruby/1.9.1/net/ftp.rb:323:in `sendcmd'
    from /usr/lib/ruby/1.9.1/net/ftp.rb:746:in `delete'
........