Use tempest_cloud_name in tempestconf

Currently on doing tempest_use_tempestconf to true, It depends on
keystone specific parameters which is not defined in os_tempest
role leading to undefined variables. Since os_tempest has nice
support of clouds.yaml for all tempest resource creation,
tempestconf also have the same and almost all openstack installers
have the same. Let's use it the same in python-tempestconf for
generating tempest.conf.

Change-Id: I498a3362ec917a3d6c9c67986770e623e6cefec2

defaults/main.yml

@@ -316,6 +316,7 @@ tempest_tempestconf_pip_packages:
 tempest_tempestconf_profile:
   debug: true
   create: true
+  os-cloud: "{{ tempest_cloud_name }}"
   out: "{{ tempest_workspace }}/etc/tempest.conf"
   network-id: "{{ tempest_neutron_public_network_id }}"
   overrides:

tasks/tempestconf.yml

@@ -42,13 +42,7 @@
     if [ -d {{ tempest_tempestconf_venv_bin }} ]; then
     . {{ tempest_tempestconf_venv_bin }}/activate
     fi
-    export OS_AUTH_URL="{{ keystone_service_internaluri }}"
-    export OS_IDENTITY_API_VERSION="3"
-    export OS_USERNAME="{{ keystone_admin_user_name }}"
-    export OS_PROJECT_NAME="{{ keystone_admin_tenant_name }}"
     discover-tempest-config --profile "{{ tempest_workspace }}/etc/profile.yaml"
-  environment:
-    OS_PASSWORD: "{{ keystone_auth_admin_password }}"
   args:
     chdir: "{{ tempest_workspace }}"
     executable: /bin/bash