Refactor OpenStack services to use default OkCodes
diff --git a/openstack/blockstorage/v1/apiversions/requests.go b/openstack/blockstorage/v1/apiversions/requests.go
index f5a793c..5b213db 100644
--- a/openstack/blockstorage/v1/apiversions/requests.go
+++ b/openstack/blockstorage/v1/apiversions/requests.go
@@ -17,7 +17,6 @@
 func Get(client *gophercloud.ServiceClient, v string) GetResult {
 	var res GetResult
 	_, res.Err = client.Request("GET", getURL(client, v), gophercloud.RequestOpts{
-		OkCodes:      []int{200},
 		JSONResponse: &res.Body,
 	})
 	return res
diff --git a/openstack/blockstorage/v1/snapshots/requests.go b/openstack/blockstorage/v1/snapshots/requests.go
index 1b313a6..cb1fd51 100644
--- a/openstack/blockstorage/v1/snapshots/requests.go
+++ b/openstack/blockstorage/v1/snapshots/requests.go
@@ -78,9 +78,7 @@
 // Delete will delete the existing Snapshot with the provided ID.
 func Delete(client *gophercloud.ServiceClient, id string) DeleteResult {
 	var res DeleteResult
-	_, res.Err = client.Request("DELETE", deleteURL(client, id), gophercloud.RequestOpts{
-		OkCodes: []int{202, 204},
-	})
+	_, res.Err = client.Request("DELETE", deleteURL(client, id), gophercloud.RequestOpts{})
 	return res
 }
 
@@ -89,7 +87,6 @@
 func Get(client *gophercloud.ServiceClient, id string) GetResult {
 	var res GetResult
 	_, res.Err = client.Request("GET", getURL(client, id), gophercloud.RequestOpts{
-		OkCodes:      []int{200},
 		JSONResponse: &res.Body,
 	})
 	return res
diff --git a/openstack/blockstorage/v1/volumes/requests.go b/openstack/blockstorage/v1/volumes/requests.go
index e67ba10..ad4e574 100644
--- a/openstack/blockstorage/v1/volumes/requests.go
+++ b/openstack/blockstorage/v1/volumes/requests.go
@@ -94,9 +94,7 @@
 // Delete will delete the existing Volume with the provided ID.
 func Delete(client *gophercloud.ServiceClient, id string) DeleteResult {
 	var res DeleteResult
-	_, res.Err = client.Request("DELETE", deleteURL(client, id), gophercloud.RequestOpts{
-		OkCodes: []int{202, 204},
-	})
+	_, res.Err = client.Request("DELETE", deleteURL(client, id), gophercloud.RequestOpts{})
 	return res
 }
 
@@ -106,7 +104,6 @@
 	var res GetResult
 	_, res.Err = client.Request("GET", getURL(client, id), gophercloud.RequestOpts{
 		JSONResponse: &res.Body,
-		OkCodes:      []int{200},
 	})
 	return res
 }
diff --git a/openstack/blockstorage/v1/volumetypes/requests.go b/openstack/blockstorage/v1/volumetypes/requests.go
index 6fedaa6..451f5be 100644
--- a/openstack/blockstorage/v1/volumetypes/requests.go
+++ b/openstack/blockstorage/v1/volumetypes/requests.go
@@ -45,7 +45,6 @@
 	}
 
 	_, res.Err = client.Request("POST", createURL(client), gophercloud.RequestOpts{
-		MoreHeaders:  client.AuthenticatedHeaders(),
 		OkCodes:      []int{200, 201},
 		JSONBody:     &reqBody,
 		JSONResponse: &res.Body,
@@ -56,10 +55,7 @@
 // Delete will delete the volume type with the provided ID.
 func Delete(client *gophercloud.ServiceClient, id string) DeleteResult {
 	var res DeleteResult
-	_, res.Err = client.Request("DELETE", deleteURL(client, id), gophercloud.RequestOpts{
-		MoreHeaders: client.AuthenticatedHeaders(),
-		OkCodes:     []int{202},
-	})
+	_, res.Err = client.Request("DELETE", deleteURL(client, id), gophercloud.RequestOpts{})
 	return res
 }
 
@@ -68,8 +64,6 @@
 func Get(client *gophercloud.ServiceClient, id string) GetResult {
 	var res GetResult
 	_, err := client.Request("GET", getURL(client, id), gophercloud.RequestOpts{
-		MoreHeaders:  client.AuthenticatedHeaders(),
-		OkCodes:      []int{200},
 		JSONResponse: &res.Body,
 	})
 	res.Err = err