Rename reclass parameter for tempest log_file setting

This parameter isn't used yet, so it's safe to rename it now.

Change-Id: I714cfddf74da1a41948a3f82297817863ee1321f
diff --git a/metadata/service/tempest/init.yml b/metadata/service/tempest/init.yml
index b9dbe3c..9996b85 100644
--- a/metadata/service/tempest/init.yml
+++ b/metadata/service/tempest/init.yml
@@ -23,7 +23,7 @@
     tempest_test_target: cfg01*
     runtest_tempest_cfg_dir: /root/test/
     runtest_tempest_cfg_name: tempest_generated.conf
-    runtest_tempest_log_dir: /home/rally/test/tempest.log
+    runtest_tempest_log_file: /home/rally/test/tempest.log
     runtest_tempest_public_net: public
   runtest:
     enabled: true
@@ -44,7 +44,7 @@
       cfg_dir: ${_param:runtest_tempest_cfg_dir}
       cfg_name: ${_param:runtest_tempest_cfg_name}
       DEFAULT:
-        log_file: ${_param:runtest_tempest_log_dir}
+        log_file: ${_param:runtest_tempest_log_file}
       compute:
         build_timeout: 600
         min_microversion: 2.1