Add support for forced delete

Signed-off-by: Ian Duffy <ian.x.duffy@aib.ie>
diff --git a/openstack/compute/v2/servers/requests.go b/openstack/compute/v2/servers/requests.go
index f9839d9..8e60daa 100644
--- a/openstack/compute/v2/servers/requests.go
+++ b/openstack/compute/v2/servers/requests.go
@@ -303,6 +303,17 @@
 	return res
 }
 
+func ForceDelete(client *gophercloud.ServiceClient, id string) ActionResult {
+	var req struct {
+		ForceDelete string `json:"forceDelete"`
+	}
+
+	var res ActionResult
+	_, res.Err = client.Post(actionURL(client, id), req, nil, nil)
+	return res
+
+}
+
 // Get requests details on a single server, by ID.
 func Get(client *gophercloud.ServiceClient, id string) GetResult {
 	var result GetResult