ActiveMQ standalone script doesn't return with 0 when stop is called.

I was testing to see if the ./bin/activemq script was LSB compatible (I want to integrate activemq into a pacemaker setup).

When calling ./bin/activemq stop, the script should return 0 on success.

The problem is in the invokeJar function. In the 'stop' case , the value of RET is set in the context of a forked process.
The proposed fix, is identical to how RET is handled in the other 2 cases.