Expose config for timeout of resource deletion

The users who run rally in CI or periodically would like this option,
because they could config this under different cases.

Change-Id: I6fd70eb5565aeeb0442475439633baf2f441d174
Partial-Bug: #1469622

etc/rally/rally.conf.sample

@@ -495,6 +495,16 @@
 #ec2_server_boot_poll_interval = 1.0
 
 
+[cleanup]
+
+#
+# From rally
+#
+
+# A timeout in seconds for deleting resources (integer value)
+#resource_deletion_timeout = 600
+
+
 [database]
 
 #

rally/plugins/openstack/context/cleanup/base.py

@@ -13,12 +13,27 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+
+from oslo_config import cfg
+
 from rally.task import utils
 
 
+CONF = cfg.CONF
+
+CLEANUP_OPTS = [
+    cfg.IntOpt("resource_deletion_timeout", default=600,
+               help="A timeout in seconds for deleting resources")
+]
+cleanup_group = cfg.OptGroup(name="cleanup", title="Cleanup Options")
+CONF.register_group(cleanup_group)
+CONF.register_opts(CLEANUP_OPTS, cleanup_group)
+
+
 def resource(service, resource, order=0, admin_required=False,
              perform_for_admin_only=False, tenant_resource=False,
-             max_attempts=3, timeout=600, interval=1, threads=20):
+             max_attempts=3, timeout=CONF.cleanup.resource_deletion_timeout,
+             interval=1, threads=20):
     """Decorator that overrides resource specification.
 
     Just put it on top of your resource class and specify arguments that you