Fusion entities table for agent_base_url
agent_base_url in configuration not editable
agent_base_url editable in entity
Send entity agent_base_url to an agent

Fetch URL from entity configuration
If unsuccessfull, use URL defined in global configuration

Log URL used in pluginFusioninventory-agent-url.log file if extra-debug
is configured.
Allow agent base URL to be displayed in entities table
Update unit test for url for entity. references #2696
Define and use agent_url_base in entity. closes #2696