RFR(XS): JDK-8067232 - [TESTBUG] runtime/CheckEndorsedAndExtDirs/EndorsedExtDirs.java fails with ClassNotFoundException

[Mikhailo Seledtsov]

     Please review this simple fix to the test.
     JBS: https://bugs.openjdk.java.net/browse/JDK-8067232
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8067232/webrev.00/
     Testing:
         Ran the test via JT-Reg locally (Linux-x64)