RFR (S) 8057936: java.net.URLClassLoader.findClass uses exceptions in control flow

[Claes Redestad]

Hi,

please review this simple patch to avoid raising PrivilegedActionExceptions
when failing to find a class in URLClassLoader.

 bug: https://bugs.openjdk.java.net/browse/JDK-8057936
 webrev: http://cr.openjdk.java.net/~redestad/8057936/webrev.2/

/Claes