Update provider_client.go

This change prevents errors "error waiting for instance to become ready" while deploying VMs in Openstack 
(when using Terraform, which requires gophercloud to talk to OpenStack)
diff --git a/provider_client.go b/provider_client.go
index e813e0e..99d9c4a 100644
--- a/provider_client.go
+++ b/provider_client.go
@@ -177,6 +177,9 @@
 		}
 	}
 
+	// Set connection parameter to close the connection immediately when we've got the response
+	req.Close = true
+	
 	// Issue the request.
 	resp, err := client.HTTPClient.Do(req)
 	if err != nil {