decode format string using 'string-escape'

decode format string using 'string-escape' required to specify format string in shell.

Without decode:
```bash
$ lc-node-list -f "%(id)s\t%(name)s\t%(ip)s"
111111\tmynode1\t192.168.1.1
111112\twebserver\t192.168.1.2
None\tdb1\t192.168.1.3
None\tdb2\t192.168.1.4
```

With decode:
```bash
$ lc-node-list -f "%(id)s\t%(name)s\t%(ip)s"
111111 mynode1  192.168.1.1
111112 twebserver   192.168.1.2
None   db1   192.168.1.3
None   db2   192.168.1.4
```