Add segments client

Segments client is necessary to test the routed provider networks
feature.
the following client methods are now available for Tempest:
* create_segment
* update_segment
* show_segment
* delete_segment
* list_segments

Change-Id: Ie89468351fc9cf68ccf356d35ee9ba4b5037c499
diff --git a/releasenotes/notes/segments-client-866f02948f40d4ff.yaml b/releasenotes/notes/segments-client-866f02948f40d4ff.yaml
new file mode 100644
index 0000000..90ac3e8
--- /dev/null
+++ b/releasenotes/notes/segments-client-866f02948f40d4ff.yaml
@@ -0,0 +1,12 @@
+---
+features:
+  - |
+    Add ``segments`` client to Tempest to make possible the testing of the
+    Routed Provider Networks feature.
+    The following API calls are available for tempest from now:
+
+    * POST /segments
+    * PUT /segments/{segment_id}
+    * GET /segment/{segment_id}
+    * DELETE /segments/{segment_id}
+    * GET /segments