Improve Solr Host defaulting in the SolrCLI

There are a number of Solr CLI commands that will use a default Solr URL if none is provided, such as solr create, solr delete, solr config, etc.

Currently it defaults to "http://localhost:8983", however we can do better by looking at the SOLR_SCHEME, SOLR_TOOLS_HOST and SOLT_PORT envVars, that the script provides us. This allows users to set their env vars, and just use these commands to interact with the solr instance that was setup, without having to manually set a URL.