Make JDK byte code verification bug workaround Java 8 compatible

A workaround for a JDK bug that affects PowerMock only work with Java 7.
The -UseSplitVerifier option is no longer supported in Java 8. As an
alternative workaround, this patch disables the byte code verifier
entirely. Since this is only used with our own unit tests, the impact
is low.

Target: trunk
Request: 2.10
Request: 2.9
Request: 2.8
Request: 2.7
Request: 2.6
Require-notes: no
Requier-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: https://rb.dcache.org/r/7197/