After tightening up JMX security in 2.1.4 by making cassandra by default only accept JMX connections from the same host, the option "LOCAL_JMX" was added to cassandra-env.sh to override this.
But, the option was added in such a way that there is no way to override it (on debian) through the /etc/default/cassandra file like other options (such as MAX_HEAP_SIZE etc).
Since cassandra-env.sh contains a lot of logic, patching it means having to maintain your patches when upgrading, making automation more work. The attached patch makes it possible to override it externally like other options, and keeping the local configuration separate from cassandra-env.sh.
(Shell-code-change tries to mimic the existing pattern in cassandra-env.sh)