RFR: JDK-8217777 TEST_BUG: jdk/java/util/prefs/ExportSubtree.java passes even when test should fail

[Steve Groeger]

Hi all, 

I have found an issue with the jdk/java/util/prefs/ExportSubtree.java 
test.
Using jtreg to run this test the test passes no matter what happens within 
the test.
Have raised an issue for this:  
https://bugs.openjdk.java.net/browse/JDK-8217777

I think the issue is 2 fold:
1) the test check the expected vs. actual and throws an exception but this 
is caught later in the code, which causes the test to pass as there is no 
exception thrown.
2) the exported XML now contains a `standalone="no"` entry in the XML 
prologue, which is not in the expected XML.

I have generated a webrev to resolve this:  
http://cr.openjdk.java.net/~sgroeger/8217777/webrev.00/

This occurs on jdk11 but is probabaly also an issue on other releases ie 
jdk8u, jdk12, jdk  etc

Please could someone review this webrev and sponsor this chnage for me as 
I am unable to commit this myself. 

Thanks
Steve Groeger
IBM Runtime Technologies
Hursley, Winchester
Tel: (44) 1962 816911  Mobex: 279990  Mobile: 07718 517 129
Fax (44) 1962 816800
Lotus Notes: Steve Groeger/UK/IBM
Internet: groeges at uk.ibm.com

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
741598. 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU