text: Title: Weaviate: Add more robust method to detect existing index
  Body: **Is your feature request related to a problem? Please describe.**
  An index should be considered as exist when there is a schema with the exist name and properties.
  
  
  **Describe the solution you'd like**
  Use the client's `exists` instead of `contains` method to detect an existing index name.
  
  **Describe alternatives you've considered**
  NA
  
  **Additional context**
  Wait for weaviate/weaviate-python-client#232 to be implemented
  