fix acceptance tests and prevent decoding empty responses
diff --git a/openstack/blockstorage/v2/extensions/volumeactions/results.go b/openstack/blockstorage/v2/extensions/volumeactions/results.go
index c767307..65778e5 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/results.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/results.go
@@ -11,22 +11,22 @@
 
 // AttachResult contains the response body and error from a Get request.
 type AttachResult struct {
-	commonResult
+	gophercloud.ErrResult
 }
 
 // DetachResult contains the response body and error from a Get request.
 type DetachResult struct {
-	commonResult
+	gophercloud.ErrResult
 }
 
 // ReserveResult contains the response body and error from a Get request.
 type ReserveResult struct {
-	commonResult
+	gophercloud.ErrResult
 }
 
 // UnreserveResult contains the response body and error from a Get request.
 type UnreserveResult struct {
-	commonResult
+	gophercloud.ErrResult
 }
 
 // InitializeConnectionResult contains the response body and error from a Get request.
@@ -36,7 +36,7 @@
 
 // TerminateConnectionResult contains the response body and error from a Get request.
 type TerminateConnectionResult struct {
-	commonResult
+	gophercloud.ErrResult
 }
 
 // Extract will get the Volume object out of the commonResult object.
@@ -46,7 +46,6 @@
 	}
 
 	var res map[string]interface{}
-
 	err := mapstructure.Decode(r.Body, &res)
 
 	return res, err