[CLI] Add support for emtpy deployment

If no platform is used config is looking like {} and it actually
doesn't make any sense to force someone to create file for that

This patch allows to create a empty deployment if there is no
--filename and --fromenv arguments

Change-Id: I15ca37fdf74b153cc2727b6293b841de42227e9f

tests/ci/rally_self_job.sh

@@ -22,7 +22,6 @@ fi
 RND=$(head /dev/urandom | tr -dc a-z0-9 | head -c 5)
 TMP_RALLY_CONF="/tmp/self-rally-$RND.conf"
 TMP_RALLY_DB="/tmp/self-rally-$RND.sqlite"
-TMP_RALLY_DEPLOYMENT="/tmp/self-rally-dep-$RND.json"
 DBCONNSTRING="sqlite:///$TMP_RALLY_DB"
 RALLY="rally --config-file $TMP_RALLY_CONF"
 
@@ -32,8 +31,7 @@ sed -i.bak "s|#connection =.*|connection = \"$DBCONNSTRING\"|" $TMP_RALLY_CONF
 rally --config-file $TMP_RALLY_CONF db create
 
 # Create self deployment
-echo '{}' > $TMP_RALLY_DEPLOYMENT
-$RALLY -d deployment create --file=$TMP_RALLY_DEPLOYMENT --name=self
+$RALLY -d deployment create --name=self
 
 # Run task
 $RALLY -d --plugin-paths=$PLUGIN_PATHS task start $TASK_FILE

tests/functional/test_cli_deployment.py

@@ -43,6 +43,11 @@ class DeploymentTestCase(unittest.TestCase):
               "--filename /tmp/.tmp.deployment")
         self.assertIn("t_create_file", rally("deployment list"))
 
+    def test_create_empty(self):
+        rally = utils.Rally()
+        rally("deployment create --name t_empty")
+        self.assertEqual("{}", rally("deployment config"))
+
     def test_config(self):
         rally = utils.Rally()
         rally.env.update(utils.TEST_ENV)