org.jboss.arquillian.container.spi.client.protocol.metadata.JMXContext should close the JMXConnector when use of MBeanServerConnection is complete

The AS7 testsuite started experiencing "JMX server connection timeout 552" threads accumulating during the AS7 testsuite run. If the testsuite runs fast enough, this seems to cause "OutOfMemoryError: unable to create new native thread" errors near the end of the testsuite run.

This doesn't recreate for everyone but it does for me.

To fix this, I think we need to keep the JMXConnector returned from calling JMXConnectorFactory.connect() until we are done with the MBeanServerConnection and call JMXConnector.close() then.