Looks like the script is barfing on the command line you have provided. Try using the following in your ossec_servers.conf:
###
### Remote server, with SSH key-based authentication and sudo
###
[ossecserver.tamu.edu]
MANAGE_AGENTS = ssh splunk@ossecserver.tamu.edu -t 'sudo /var/ossec/bin/manage_agents'
AGENT_CONTROL = ssh splunk@ossecserver.tamu.edu -t 'sudo /var/ossec/bin/agent_control -l'
... View more