Some options should not be searched for in the salt-cloud global config
Some options should not be searched for in the salt-cloud global config
Also test if the VM defined provider is present in the loaded provider configs.
Fix `_vm_provider()`. Non global options.

* Fixed a bug which did not allow `_vm_provider()` to produce results coherent with the new configurations syntax.
* Some options should not be searched for in the salt-cloud global config.
Some options should not be searched for in the salt-cloud global config
Fix bug introduced in the initial syntax migration. Non global options.

* Some options should not be searched for in the salt-cloud global configuration.
Some options should not be searched for in the salt-cloud global config.
Some options should not be searched for in the salt-cloud global config.
Some options should not be searched for in the salt-cloud global config.
Some options should not be searched for in the salt-cloud global config.
Some options should not be searched for in the salt-cloud global config.
Some options should not be searched for in the salt-cloud global config.
Some options should not be searched for in the salt-cloud global config.