These errors appear as the Web Agent tries to load a plugin defined in configuration, and it is not able to load it. As the plugin is shown in the messages as '', it could mean there is an incorrect setting in the WebAgent.conf file or ACO configuration.
If we check the Web Agent startup process, we can see it is actually loading an empty loadplugin parameter:
[24718/671680832][Wed Aug 23 2017 02:27:20] loadplugin='/software/ca/httpd-delivery/webagent/bin/libHttpPlugin.so'.
[24718/671680832][Wed Aug 23 2017 02:27:20] loadplugin=''.