Create scenario tests for loadbalancers

This patch implements the tempest plugin for basic load balancer
operations in Octavia. It contains tests for loadbalancer API and
a minimal operation test for loadbalancing functionality.

Steps for testing in devstack environment:

- Clone octavia-tempest-plugin repo, check out this patch, install
  octavia-tempest-plugin project.
- Create a tempest work directory by running 'tempest init <workdir>'.
  In the etc/tempest.conf, add 'loadbalancer = true' in
  'service_available' section.
- Set a big value to 'OS_TEST_TIMEOUT' in .testr.conf
- Add or modify other related config options (image, network, flavor,
  validation, etc).
- Run 'tempest run --regex ^octavia_tempest_plugin'

Co-Authored-By: Lingxian Kong <anlin.kong@gmail.com>
Co-Authored-By: Adam Harwell <flux.adam@gmail.com>
Change-Id: Ibc2904f431b15dfca2ff8e38e0d4d06c1430abea
diff --git a/requirements.txt b/requirements.txt
index 6de9f4e..70c84fe 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,4 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-pbr!=2.1.0,>=2.0.0 # Apache-2.0
+pbr>=2.0.0,!=2.1.0  # Apache-2.0
+oslotest>=1.10.0  # Apache-2.0
+tempest>=17.1.0  # Apache-2.0
+tenacity>=3.2.1  # Apache-2.0