Stop adding ServiceAvailable group option

Service available group already exists.Therefore we don't need to
register this group here again.

Change-Id: I2096ed1f69a1f70fbf248fee5fded94e3caca6c6
Closes-Bug: #1621036

watcher_tempest_plugin/config.py

@@ -17,11 +17,7 @@
 from oslo_config import cfg
 
 
-service_available_group = cfg.OptGroup(name="service_available",
-                                       title="Available OpenStack Services")
-
-ServiceAvailableGroup = [
-    cfg.BoolOpt("watcher",
-                default=True,
-                help="Whether or not watcher is expected to be available"),
-]
+service_option = cfg.BoolOpt("watcher",
+                             default=True,
+                             help="Whether or not watcher is expected to be "
+                                  "available")