Rename around existing knife option.

Awesome plugin, thanks for putting this together.

Ran into an issue in running

```
knife backup export -d pre_cleanup
```

my results got placed in .chef/chef_server_backup. Looks like the cause is that knife from chef 11.4.0 already specifies a -d option:
```
    -d, --disable-editing            Do not open EDITOR, just accept the data as is
```
pull renames it to -D.