Apply a naming rule of GET to compute clients(l*)

[GET /resources] methods should be "list_<resource name>s"
or "show_<resource name>", so this patch applies the rule
to compute clients which name is "limits".

Partially implements blueprint consistent-service-method-names

Change-Id: Ibe30d01057936cea68f38984064dff107cdcbe5c
diff --git a/tempest/cmd/cleanup_service.py b/tempest/cmd/cleanup_service.py
index eb6f143..4dc03f9 100644
--- a/tempest/cmd/cleanup_service.py
+++ b/tempest/cmd/cleanup_service.py
@@ -377,7 +377,7 @@
 
     def dry_run(self):
         client = self.limits_client
-        quotas = client.get_absolute_limits()
+        quotas = client.show_limits()
         self.data['compute_quotas'] = quotas