Fix coverage test

1. We should use the report in `cover` directory instead of `cover-master`.
2. simplify job definiton base on tox-cover.

Change-Id: Ic32d556b4e191c594384f7f604e4b4ff46ccf317

.zuul.d/zuul.yaml

@@ -30,14 +30,14 @@
 
 - job:
     name: rally-tox-cover
-    parent: tox
+    parent: tox-cover
     description: |
       Run test for rally project.
 
       Uses tox with the ``cover`` environment.
     vars:
-      tox_envlist: cover
-    post-run: tests/ci/playbooks/post-rally-coverage.yaml
+      coverage_output_src: '{{ zuul.project.src_dir }}/cover/'
+      zuul_executor_dest: '{{ zuul.executor.log_root }}/coverage/'
 
 - project:
     check:

tests/ci/playbooks/post-rally-coverage.yaml

@@ -1,15 +0,0 @@
-- hosts: all
-  tasks:
-
-    - name: Put coverage report in the right place
-      synchronize:
-        src: "{{ zuul.projects['git.openstack.org/openstack/rally-openstack'].src_dir }}/cover-master/"
-        dest: '{{ zuul.executor.log_root }}/coverage/'
-        mode: pull
-        copy_links: true
-        verify_host: true
-        rsync_opts:
-          - --include=/**
-          - --include=*/
-          - --exclude=*
-          - --prune-empty-dirs