Pin container to 9.3

Author: ljstella

contentctl.yml

@@ -21,8 +21,8 @@ test_instance:
   hec_port: 8088
   web_ui_port: 8000
   api_port: 8089
-  full_image_path: registry.hub.docker.com/splunk/splunk:latest
 container_settings:
+  full_image_path: registry.hub.docker.com/splunk/splunk:9.3
   leave_running: true
   num_containers: 1
 mode: {}