By default SNMP4J simply throws away it's logs, and it would be good if it sent them to Log4J by default so that they can be enabled just by editing jboss-log4j.xml. Currently you have to edit rhq-server.sh and restart JON to enable it.
To send SNMP4J logs to log4j, you can either add "-Dsnmp4j.LogFactory=org.snmp4j.log.Log4jLogFactory" to the RHQ java opts, or call LogFactory.setLogFactory(new org.snmp4j.log.Log4jLogFactory()) in code.
If this change is made, setting the org.snmp4j category to WARN (or ERROR) by default is probably a good idea.
i think as a quick workaround, you can add that system property to rhq-server.properties
Assuming workaround is sufficient.