Feature/filestorage sharenetworks get (#125)

* sfs: Add get for share networks

* sfs: Add acceptance test for share network Get

* sfs: Improve unit test for share network Get
diff --git a/openstack/sharedfilesystems/v2/sharenetworks/results.go b/openstack/sharedfilesystems/v2/sharenetworks/results.go
index 8086508..ce2b00b 100644
--- a/openstack/sharedfilesystems/v2/sharenetworks/results.go
+++ b/openstack/sharedfilesystems/v2/sharenetworks/results.go
@@ -137,3 +137,8 @@
 type DeleteResult struct {
 	gophercloud.ErrResult
 }
+
+// GetResult contains the response body and error from a Get request.
+type GetResult struct {
+	commonResult
+}