Add a scenario test for spare pool

This patch adds a scenario test for testing amphora spare pool feature.
It adds new check jobs to test against master as well as stable
branches.

Change-Id: I87249017453628e3d2cd320a02677d81397f1b26
diff --git a/octavia_tempest_plugin/config.py b/octavia_tempest_plugin/config.py
index 425ad60..67898a0 100644
--- a/octavia_tempest_plugin/config.py
+++ b/octavia_tempest_plugin/config.py
@@ -185,4 +185,8 @@
                default="TCP",
                help="The type of L4 Protocol which is supported with the "
                     "provider driver."),
+    cfg.StrOpt('spare_pool_enabled',
+               default=False,
+               help="Wether spare pool is available with amphora provider "
+                    "driver or not."),
 ]