The --container option of the freezer-agent should be set 'None' as default

When the swift storage is specified with --storage swift, the container will be used as container name,
when the ssh or local storage is specified with --storage ssh or --storage local, the container will be used as path.
They are different. The container should be set "None" as default.

Scenario 1:
The local storage is specified with --storage local, if the freezer-agent is executed without --container in a directory, the default container name "freezer_backups" will be used as directory name, the directory "freezer_backups" will be created in the current directory.

if the current directory is same as --path-to-backup, you will be notified with an error.

Scenario 2:
The local storage is specified, Create a job without --container, the default container name will be used as directory name.

When the job is being executed, the "freezer_backups" directory will be created in the current directory(/usr/local/bin/ or similar directory). The "Permission denied" error will be raised.

Scenario 3:
Restore data without --container option, for example:
freezer-agent --action restore --restore-abs-path /home/zhusz/freezerclient-restore/ --backup-name backup-test --storage local

The default container name "freezer_backups" will be used as directory.
The freezer-agent will restore data from directory "freezer_backups".
you will be notified with an error "Critical Error: No matching backup name "ubuntu_backup-test" found".