Description of problem:
When EAP 7.2 standalone is running on jdk11 the configuration shown in JON UI is broken due to:
The following configuration properties have invalid values: [Ext Dirs]. The values must be corrected before the configuration can be saved.

Version-Release number of selected component (if applicable):
JON 3.3.11 + EAP plugin pack 08.CR01

How reproducible:
Always

Steps to Reproduce:
1. install openjdk 11 and set JAVA_HOME env variable (e.g. export JAVA_HOME=/usr/lib/jvm/java-11-openjdk)
2. also install openjdk1.8 for agent and set RHQ_AGENT_JAVA_HOME (e.g. export RHQ_AGENT_JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-7.b13.el7.x86_64/jre)
3. install/start/register agent
4. start EAP 7.2 standalone (jboss-eap-7.2/bin/standalone.sh &)
5. import the EAP from discovery queue
6. run Install RHQ User operation
7. navigate to EAP 7.2 standalone resource -> Configuration

Actual results:
Following err msg is shown in UI:
The following configuration properties have invalid values: [Ext Dirs]. The values must be corrected before the configuration can be saved.

and in agent.log:
Plugin Error: Invalid EAP7 Standalone Server Resource configuration returned by EAP7 plugin - Required property 'ext-dirs' has a null value.


Expected results:
No errors.

Additional info:
Ext Dirs property is empty which is causing the error.
When the EAP is using openjdk1.8 the property is set to:
[/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-7.b13.el7.x86_64/jre/lib/ext, /usr/java/packages/lib/ext]

Workaround: Configuration is saved successfully when the Ext Dirs property is set to some dummy value.