Remove last slash in gnicchi service url

Url is returned from catalogue with trail slash, but gabbi tests cant
compare results when there are single slash in result and two slashes in
expected results.

Related-PROD: PRODX-7913
Change-Id: Ib3dda217f55d0c58391b35b06e0fe443109e223c
diff --git a/telemetry_tempest_plugin/scenario/test_gnocchi.py b/telemetry_tempest_plugin/scenario/test_gnocchi.py
index e283d2f..058e076 100644
--- a/telemetry_tempest_plugin/scenario/test_gnocchi.py
+++ b/telemetry_tempest_plugin/scenario/test_gnocchi.py
@@ -41,7 +41,8 @@
             {'service': CONF.metric.catalog_type,
              'endpoint_type': CONF.metric.endpoint_type,
              'region': CONF.identity.region})
-
+        if url[-1] == "/":
+            url = url[:-1]
         os.environ.update({
             "GNOCCHI_SERVICE_URL": url,
             "GNOCCHI_SERVICE_TOKEN": token,