You are running the agent with the -t (--test) option, which implies several other options including --no-daemonize (but not --noop). If you want to run the agent as a daemon then omit that option. Rather than launching it manually, though, it would be better to launch it via its service management script, which should have been installed as part of the package (supposing you used a package, rather than a source install). On many systems, the command would be "service puppet start".
John