RFR: 8043939 Remove management-agent.jar

[Staffan Larsen]

management-agent.jar is the java agent that is used with the attach API to start the JMX agent in a target VM. It's the approach used in JDK 6 to start JMX in a running VM and predates the "jcmd ManagementAgent.start" command added in 7uX. 

JDK-8044135 added an API in the attach framework to start the JMX agent, and it is now time to remove management-agent.jar.

webrev: http://cr.openjdk.java.net/~sla/8043939/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8043939

Thanks,
/Staffan