[eclipselink-dev] fix for bug 289930 --- modify ProxyAuthenticationServe

[Yiping Zhao <yiping.zhao@xxxxxxxxxx>]

Changes are:

1. Modify build.xml under <trunk>/jpa/eclipselink.jpa.test to add 
<sysproperty key="proxy.user.name" value="${proxy.user.name}"/>
2. Add getServerProperties() in ProxyAuthenticationServerTestSuite to 
overwrite the one defined in JUnitTestCase to  get and set value for 
"proxy.user.name" property

Note: If you want to run proxy tests on server, you need to have 
"proxy.user.name" in your test.property and set value to it.

Code is reviewed by Edwin Tang.

https://bugs.eclipse.org/bugs/show_bug.cgi?id=289390

Thanks,
Yiping