Skip tests for production environment

Allow tests for production in cases:
- Tests that do CRUD for tlds
    * pre-created testing TLDs

- Tests that use TLDs for creating zones
    * list of TLDs is empty
    * pre-created testing TLDs

Related-Prod: PRODX-29973
Change-Id: Ifcaa5115ad4e279ad70e7feb44b82a34e10d2a71
diff --git a/designate_tempest_plugin/config.py b/designate_tempest_plugin/config.py
index 2a8e25e..0473dfd 100644
--- a/designate_tempest_plugin/config.py
+++ b/designate_tempest_plugin/config.py
@@ -54,7 +54,10 @@
                     "If it is not specified, a new zone will be created "),
     cfg.StrOpt('tld_suffix',
                default='test',
-               help="TLD suffix that used in all tests (if not overridden).")
+               help="TLD suffix that used in all tests (if not overridden)."),
+    cfg.ListOpt('existing_tlds',
+               default=[],
+               help="List of current TLDs created on the environment"),
 ]
 
 dns_feature_group = cfg.OptGroup(name='dns_feature_enabled',