RFR: 8150145: javax/xml/jaxp/unittest/common/TransformationWarningsTest.java and ValidationWarningsTest.java failed intermittently without any error message

[Aleks Efimov]

Hello,

Please, help to review the tests fix.
Webrev: http://cr.openjdk.java.net/~aefimov/8150145/00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8150145

The list of changes:
1. Two tests were modified to print exception occurred during execution. 
Before that these tests were failing silently.
2. The tests were slightly modified to correctly run with security 
manager run mode recently added to JAXP tests (JDK-8067170).
3. TransformationWarningsTest were modified to synchronize the 
TransformerFactory instantiation.

The modified tests were executed 2000+ times (alongside to other tests 
from jaxp/test/javax/xml/jaxp/unittest/common) on linux-x64 and there 
were no failures observed. According to this result and that the tests 
were modified not to fail silently. I would like to remove these two 
tests from the jaxp problem list.
If the tests will continue to fail on some configurations (JPRT shows no 
failures for few runs though) the proposed changes will help to diagnose 
the cause of failures.

With Best Regards,
Aleksej