Api v2 management allows swagger config to have basepath and path both set to /

When creating a new api, a swagger is sent to api management with both base path and operation path set to `/` the API doesn't error out.

To reproduce you should could use the WSK CLI
```
wsk api create / / get myaction
```
```
wsk api list -f
Action: /guest/myaction
API Name: /
Base path: /
Path: /
Verb: get
URL: https://service.eu.apiconnect.ibmcloud.com/gws/apigateway/api/123/
```
api management doesn't return error to know that there is an invalid combination to have both base path and operation path set to `/`

Reproduce the issue with the WSK CLI command `wsk api create / / get myaction`, then inspect the API v2 management path that handles the generated Swagger configuration. Confirm the behavior with `wsk api list -f`; done means the invalid combination of base path `/` and operation path `/` is rejected with an error.

Written by the indexing model from the issue text.