RFR(XS): 8048050: Agent NullPointerException when rmi.port in use

[Sergey Gabdurakhmanov]

Hi,

Could I please have a review of this small fix.

webrev: http://cr.openjdk.java.net/~sgabdura/8048050/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8048050

Problem description:
If the com.sun.management.jmxremote.rmi.port option is provided it will 
give a NPE if already in use by a different JVM. Its expected to fail 
but should provide an appropriate exception.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run two instances in different JVMs at same time with the following 
options:
-Dcom.sun.management.jmxremote.port=2222 
-Dcom.sun.management.jmxremote.rmi.port=2223 
-Dcom.sun.management.jmxremote.authenticate=false

Root cause:
Then we trying to start JMXConnectorServer (see method exportMBeanServer 
of class sun.management.jmxremote.ConnectorBootstrap on already used 
port it cause IOException. Call of connServer.getAddress().toString() in 
the exception handler cause NullPointerException because 
connServer.getAddress() returns null.

Solution:
Provide url.toString() if connServer.getAddress() is null

I'm going to push this fix into JDK9, 8 and 7.

BR,
Sergey